Imperial Races Codex Entry

Imperial Races:
While the orginal Imperium was almost exclusively made up of humans as it expanded and brought other races into its folds the Imperium's ethnic diversity exploded.  Over a million known dialects are spoken within the Imperium and countless species are now proud members of the Imperium.  These races include Human, Near-Human, Eldar, Near-Eldar, Tau, Asari, Salarian, Turian, Volus, Elcor, Drell, Hanar, Quarians, Krogan, Sangheili, Huragok, Lekgolo, Yanme'e, Kig-Yar, Unggoy, Equine, and many many others others.

Human-
Humanity is the dominate species within the Imperium with over fifty two percent of the total population.  In ancient times humanity waged a war against the Forerunners and the Flood Parasite.  This original human empire was defeated by the Forerunners and forcibly regresses both culturally and technologically to the stone age.  
However the Forerunners realized their grave error as the Flood began to overwhelm them.  With the Repear threat also now in full swing the Forerunners enacted a desperate gamble to preserve humanity to serve as their heirs, designated as Reclaimers granting humans access to all of their technology.  They proceeded to destroy many of the mass relays in the orion arm of the galaxy to ensure that humanity would not fall so easily into the Reapers trap.  They then moved both humanity and all other sentient species to the Ark before activating the Halo array and destroyed themselves, containing the Flood for the time being.  Humanity would be scattered across the Orion arm on countless worlds to give the species as great a chance of success as possible.
The humans of the world Terra were the first to begin reinvesting themselves in the stars establishing countless colony worlds and entering a golden age of technology and commerce.  However the event known as the Fall of the Eldar would produce devestating warp storms that scattered and destroyed this new human empire.  It would be thousands of years before the God Emperor of Mankind would reunited the warring tribes on Terra and begin the great crusade to reclaim the galaxy.
Other humans from the world of Coruscant rose to promince in this time.  With the fall of the Rakata Empire during the birth of the Chaos God Slaanesh the humans of Coruscant would expand across the galaxy and estabish the Galactic Republic.  It was they who would ally with the Jedi order and bring countless aliens and near humans into their government.
The humans of Earth, the original birth place of humanity would be the last to join their brothers in space.  Yuri Gagarin was the first human from Earth in over a hundred thousand years to break free of the planets atmosphere.  Within the decade Neil Armstrong would be the first to walk on the Moon.  
However Earth's expansion into space was anything but pleasent as war broke out between Earth and its first colonies.  The One Year War, the first and second Bloody Valentine wars, the Rainforest wars, and countless other conflicts slowed man kinds progress.  Overcrowded, Earth's Government deported thousands of criminals to establish a long distance penal colony.  The colony ships went off course however and ended up in the distant Koprulu sector.
Humanities expansion into space was marked with further brutal wars.  The God Emperor waged the Great Crusade to reunite the lost colonies and free them from the control of hostile xeno's and the forces of chaos.  The Republic became embroiled in numerous wars with the Sith Empire which left billions dead and burned countless worlds.  Earth faced the brutal Human-Covenant war with the Covenant Empire as well as the Flood parasite, a twenty seven year long conflict for the survival of the species.  
Humanity would triumph in the face of all opposition however, and soon the great human powers came to a head.  The First Great Galactic war ensued as the various human powers and their allies battled to dominate the Orion arm.  Some battle weary refugees fled and found the world of Gaia, and their intermingled with another human population but kept their heads down for decades.   Humanity would at last unite its strength to battle the Tyranids and eventually melded all of its dispirate peoples into a single Imperium.
In the Koprulu sector humanity would rise above adversity within the space of a few centuries and began expanding to new colonies.  Before long they encounter hostile aliens, the enigmatic Protoss and the insidious Zerg swarm.  Humanity would be humbled by these aliens but not destroyed.  The Imperium eventually rediscovered the lost colonies of the Koprulu sector but failed to assert control over them, driven back by the Zerg Swarm.  The Koprulu Sector would not be brought into the Imperium until the Reaper War several years and many lives lost later.
The Refugees and humans of Gaia however would stumble upon the keys to the wider galaxy.  They found Prothean ruins and discovered the Mass Relays.  Using these they expanded until they would encounter the Citadel Council races and later join them to further peaceful expansion.  When the Imperium discovered the relays themselves they found yet another people of humans who were allied with a vast and powerful alliance of Alien species.
The Council races however were cautious of the upstart humans, many seeing them as new comers and over eager bullys willing to do anything to expand their power.  The Humans of Gaia refused to rejoin the Imperium and would endevour to join the Citadel Council.  The Imperium frustrated in its efforts refused to bow before treaties and laws that they had had no say in writing, laws that they saw as stifling to its expansion and growth.
It would take the Reapers to at last unite the Humanity as Commander John Shepard's actions gave humanity a place on the Citadel Council.  When the Reapers at last came it was humanity that would spear head the counter attack and bring the Imperium into the fray.  When Commander Shepard activated the Catalyst he ended the Reaper threat once and for all.  The Imperium then brought the Citadel Council into the fold as full equals.
Since then Humanity has entered a new golden age of expansion, industry, and cultural advancement.  Under the God Emperor's watchfull stewardship the Imperium's Economy is strong, its people confident and loyal, its armies unmatched in courage, and its power exploding through the proverbial roof.  While there are still many threats facing the Imperium and many internal problems such as poverty, pollution, and a rising wealth gap, the Imperium is stronger than it has ever been.
Humans are not the strongest, the fastest, the smartest, or the toughest species in the galaxy.  Indeed one look at humanities harsh origins would raise the question of how any species could survive such an unforgiving and brutal ordeal?  Humanities raw will power is the answer, a refusal to break in the face of adversity and an eternal willingness face new challenges, then conquer them.  A desire to bend even the most primal of forces to its will and assert its place within the cosmos as the true masters of the universe.  As a wise man once put it, "Humanty.  Fuck yeah."

Near-Human-
Near-human is a general catch all term for various alien species that have similar biology and many times physical apperance to normal humans.  Near-humans are for the most part very similar to standard humans; mamalian bipeds, with two arms and two legs.  All of them are capable of interbreeding with humans and producing off spring without serious danger complications.
However all of them break away from the standard human form in some way; unusal size or builds, additional organs, extra apendages, vestigal features such as horns, and other features.  Some might also be missing some common features for normal humans.  They are however healthy.
In the past more extreme variations from the standard human form were killed for fear of dangerous mutation.  However as time passed many became seen as usefull or acceptable.  Most Near-humans face considerably less discrimination today then they did centuries ago.  Many have become proper upstanding citizens of the Imperium.  
Well known races of Near-Humans include but are not limited to: Zeltron, Chiss, Zabrak, Ogryns, Nightsiders, Ratlings, Mirialans, Cereans, Miraluka, and many many more.

Eldar-
The Eldar are an ancient race who once dominated the Galaxy but are now few in number.  While the Eldar are capable of interbreeding with humans they are not along the same evolutionary chain having evovled seperatly from humanity.   At a glance most would classify Eldar as Near-humans however this a mistake. Superficially, the Eldar appear very similar to humans, though they are generally taller and slimmer, with sharp features and pointed ears. They are long-lived by human standards, and most will live more than a thousand years unless they die from accident or disease. Eldar also have much faster metabolic rates than humans, and their cardiac and neurological systems are more advanced. These traits manifest in their vastly heightened reactions and agility compared to humans.   The Eldar also experince emotions on an entirely seperate level from humans with greater intesity.  They are also known to more frequently produce psykers than almost any other race save for the Protoss.
Thousands of years ago the Eldar ruled the galaxy with a great empire spanning across the stars.  Using their complex webway network they were able to travel between worlds without the need of starships.  Their technology and culture was beyond anything any other species in space could achieve.
The Eldar grew proud and vain however, seeking out new thrills and ways to amuse themselves.  Their advance technology had removed almost any need for regular labor giving them limitless free time to explore their darker and baser nature.  Vile cults began to rise, acts of hedonism and depravity that leave one speechless were preformed.  
Some saw the dangers of this new path but went unheeded.  They consructed the great craftworlds to trade between their empire and escape the debauchery of their kin.  Others went even further, forsaking technology on far flung worlds well away from the sadisism and cruelty of their homeworlds, these new colonies were known as the Maiden worlds.
At last however the Eldar went to far.  In their debauchery and wicked deeds they gave birth to a new chaos god within the warp, Slaanesh.  Slaanesh's birth tore the great hole in real space known today as the Eye of Terror which consumed the Eldar home worlds and brought an end to their empire.  Slaanesh destroyed almost all of the Eldar Gods all save Khaine who was shattered into many fragments, Isha who was taken by Nurgle but later saved by the God Emperor, and Cegorah who escaped into the Webway.  Slaanesh claimed ownership of the  souls of all Eldar.
The Eldar as a species survived but were greatly changed.  Many of their Craftworlds were clear of the Eye of Terror but a few were caught in its wake and trapped.  On the Maiden worlds many more survived but over time some began to change become near Eldar rather than proper Eldar.  Still others escaped into the Webway and became the vile Dark Eldar, raiding and continuing the same acts of evil that caused the Fall.
The Eldar would remain isolationist until the rise of the Imperium.  Eldrad of Ulthwé warned the God Emperor of the dangers of Chaos and the Emperor passed this warning onto the Primarchs.  Eventually the Emperor would rescue the Goddess Isha from Nurgle earning the Eldar's gratitude and allegince.  
The Eldar are now members of the Imperium though they are still rather problematic.  Many young Eldar become Corsairs who engage in piracy attacking merchant ships and isolated colonies.  Officially the Eldar condem such acts but take little action against Corsairs due to their limited numbers and the fact they present a valuable force of experinced warriors.  
The Eldar make passable diplomats and excellent investigators due to their psychi talents.  Many join the Inquisition or special operations forces.  Eldar craftsmenship is also known for its grace and reliability being popular as luxury goods and materials.  The Eldar are highly skilled warriors but very few Eldar Imperial Guard Regiments exist due to their small numbers.  Biel-tan produces the most Eldar Guard regiments while Alaitoc produces many Rangers who are attached to Guard regiments.

Near-Eldar-
Near-Eldar refer to races descended from the Eldar mostly on the Maiden worlds.  These races are almost biologically identical to the Eldar but have been altered in various ways.  This can range from differing features to different internal structures.  Usually these adaptations are to better survive in their new enviroments.  
Some like the Asur have had very little change from the original Eldar form.  They are slim, keen senses, tall, fair skinned, long lived, elegant and graceful, and have a high affinity towards magic.  Such cases of such a pure lack of alteration are rare however as Slaanesh's birth effected all Eldar differently.
Even more rampant mutation transformed the Eldar of Azeroth into Trolls, losing much of their race and beauty.  Exposure to acrance energies however steadily reverted some back into a more Eldar like form with the Sin'dorei and Quel'dorei being the closest.  The Avariel are a race of near-eldar who have grown wings and posess a lighter body structure.  Some believe the Quarians are Near-Eldar due to physical similarities but the results of DNA and evolutionary anlyasis has been inconclusive or conflicting so the Quarians are not considered on the whole as near-eldar.
The Sephi are another race of Near-Eldar native to the regions that once made up the Galactic Republic.  The Sephi are noted for having a slight purple tint to their skin but otherwise fit comfortably in the typical model of a near Eldar race.  In the recent Clone Wars however the Sephi attempted to defect to the CIS.  The Campaign on their homeworld of Thrustra left a bad taste in the mouths of many politicians, particularly after the final statements of their late king.
Interbreeding with humans or near-humans has resulted in some Near-Eldar that may be considered near-human such as half eldar, half elves, Arkanian, and Arkanian off-shoots.  Usually the classification is based on how much they share with each parent race.  If higher eldar or near-eldar DNA is present they are classifed as near-Eldar.
The Eldar tend to have mixed relations with Near-Eldar.  As many became primitives many craftworld Eldar look down on them as such.  Others however take note of the fact that while the Eldar are dwindling the Near-Eldar are numerous enough to keep the species alive.  Many Craftworlds have sent ambassadors to these Near-Eldar races, hoping to help speed their development.

Tau-
The Tau are relative new comers to the galactic stage, only rising to power in the midst of the first Great Galactic War.  The Tau are a blue skinned species of Aliens.  They are noted for a ridged caste system, highly advanced technology, and almost no warp presence.  The Tau were discovered early in the Great Crusade but before anything could be done warp storms rolled in and prevented access to the Tau star systems.  Back then they were primitives with only the most rudimentary tools.  
Under the leadership of the rising Ethereal caste the Tau were united and began to advance rapidly.  They encountered other species such as the Kroot and Vespid and many others who they brought into their philosophy of the Greater Good.  The Tau's technology gave them initial edge when they reecounter humanity winning them many early battles against poorly organized PDF forces and colonial militias.  When humanity struck back the Tau were forced onto the defensive and quickly realized they were badly out numbered by the humans of all three powers.
When the Tyranid invasions began it was the Tau who called for an allaince to defeat them.  The Water caste diplomats of the tau were invaluable in securing the Alliance that eventually defeated the initial Tyranid Hive Fleets.  They would later be founding members of the new Imperium of Orion.
The Tau lend their aid to the Imperium in a variety of capacities.  Tau Fire Caste warriors join the Imperial Guard, Earth Caste engineers develop new weapons and equipment for the guard, the Air Caste fly ships and fighters for the Imperium, and the Water Caste provide invaluable diplomats for the Imperium.  The Ethereals are limited to only those who embrace the greater good and act as the spiritual and political leaders of the Tau people.  

Asari-
The Asari were the first species of the modern cycle to discover the Citadel.  Asari are long lived monogender race, they have natural biotics, and can interbreed with any known race, the offspring of such unions will always be Asari however.  They are also considered attractive by almost every known race in the galaxy, with the exception of the Eldar.
The Asari evolved on Thesia, their development secretly manipulated by the Protheans with the intention of uniting the races of the galaxy against the Reaper threat.  The Protheans even left the Asari a functioning beacon with massive amounts of information that were deemed nessecary to defeat the Reapers.  The Asari however ignored the warning about Reapers and instead kept the beacon a secret, using its information to develop rapidly with the most advanced technology in the galaxy.  
The Asari are natural diplomats helping to found the Citadel Council with the Salarians and later the Turians and Humans.  The Asari were frequently the compromisers of the Council, valued for their wisdom and experince.   Their diplomatic abitilies have stopped countless conflicts including the relay 314 incident or as some call it the First Contact War.
The Asari have one of the most advanced cultures in the Galaxy with Thesia having more theaters, museums, art galleries, libraries, parks, and fine restruants than any other planet in the galaxy.  They frequently have a keen interest in new species and cultures further helping their diplomatic role.
Some however see the Asari as arrogant or self absorbed Elitests.  This ego can sometimes make them difficult to work with or lead them to dangerously underestimate a threat.    
As warriors the Asari are informal, relying mostly on small militia's for defense.  Many of these small squads however are as dangerous as whole battalions of other armies being skilled a sabotage and stealth warfare.  Their own fleet was massive with some of the most advanced ships in the galaxy.  During the Reaper war however this force was no where near strong enough to halt the Reaper invasion of Thessia.  It wasn't until the Imperium formally entered the war that Thessia saw relief, with thousands of Imperial Guardsmen and Space Marines sacrificing their lives to open up an evacuation lane and tie down Reaper forces.
Following the Reaper War the Imperium absorbed all of the former Council Races including the Asari who to this day continue with their practices of diplomacy.  There are currently only three known Asari Guard regiments as Imperial Commanders found it difficult to impress upon the Asari the guards more regimented style of warfare.

Salarian-
The Salarians are a warm blooded amphibous species native to the world of Sur'kesh with a hyper active metabolism.  The Salarians are short lived but make up for it with keen intellects and fast mouths.  The Salarians were the second species to join the Citadel Council alongside the Asari.
The Salarians are brillant scientists, doctors, researchers, investigators, and spies.  Their Special Tasks Group, or STG, was used as the model for the Council Specters.  The Salarians believe that information and science are their best weapons against a hostile galaxy, they often win their wars before the enemy even knows the fighting has started.
The Salarian's brilliance has created more than its fair share of problems however.  It was the Salarians who unleashed the insectoid rachni upon the galaxy resulting in a massive war.  The Salarians then uplifted the Krogan to defeat the Rachni only for the Krogan to expand to rapidly and start yet another war.  The Salarians developed the Genophage which was used by the Turians to end the Krogan Rebellions.  The Genophage was not cured until the Reaper War.
During the Reaper war the Salarians were caught on the back foot and began to panick, survival instincts kicking in.  The Salarians provided limited support to the allied fleet until Commander Shepard saved their Councilor from a Cerberus Coup.  Sur'Kesh was never invaded properly by the Reapers though several colonies were devastated.
When the Imperium absorbed the Citadel Races the Salarians provided valuable scientific breakthroughs for the Imperium.  The STG remains active supporting the Imperial Guard.  The Salarians have provided few regiments to the Guard however as they are poorly built for large scale ground warfare.

Turian-
The militaristic, avian like Turians hail from Palaven a hard world that has breed a hard people.  The Turians have hard bodies designed to resist excess solar radiation and have dextro-amino acid based DNA, like the Quarians. The Turians were the last species to join the Citadel Council before humanity.
The Turian's were given their seat on the Council for defeating the Krogan.  The Turian's highly militarized society breeds some of the best disciplined soldiers in the galaxy.  Every Turian is a member of the military be it as an active service member or as part of the reserves.  The Turian's were th most powerful Citadel Military force and were given peace keeping duties.
It was the Turian's who first made contact with humanity when they attempted to activate a dorment Mass Relay, something that was illegal under Council Law.  The Turian's pursued the humans to the colony of Shannix which they captured after intense fighting.  When the Alliance fleet counter attacked the Turian's geared up for full scale war.  The Asari stepped in and prevented further blood shed.  Relations between humans and Turians remained mixed at best for many years.
All of that changed with the Reaper War.   The Turian Homeworld of Palaven was the only Council Homeworld attacked by the Reapers that did not fall to the enemy.  The Battle of Palaven is marked as a major turning point in the Reaper War as Turian troops held out long enough for the allied forces to be built up enough to turn the tide and drive the Reapers from the star system.  Notes from that campagin are required reading for every military academy in the Imperium now.
After the Imperium absorbed the Council races into itself the Turians found a welcome home in the Imperial Guard.  There are over two hundred regiments from Palaven alone, many have which date back thousands of years to Turian Iron Age.  Turian's are well favored by guard commanders for their discipline and unrelenting power.  Many Turian colonies have become major centers of Guard recruitment, and military production.
Some Turian's however find the Imperium distasteful or refuse to fight under human commanders.  These Turians have joined the CIS and are some of its fiercest fighters and most able strategists.   These traitor Turians are shown no mercy and no pity, only the hangmans noose or the firing squads muzzle flashes.

Other Council races-
Various other were brought into the Imperium that had previously been associate members of the Citadel Council.  The Volus, a squat race of aliens who are used to high pressure conditions have made their way into the Imperium as stock brokers, lawyers, bankers, merchants, and businessmen.  The Elcor large slow mammals who evovled on a high gravity world are well regarded for their calm reason and great strength.  The Hanar, a race of Jellyfish like creatures encountered a crisis of faith following the Repear war but have joined the Imperium as full members.  The Drell a client race of the Hanar have found a strong niche as assassins, spies, and snipers for the Imperium.
The Krogan were instrumental in defeating the Reapers and once the war was over found a welcome home in the Imperium.  The Imperial Guard provided an excellent outlet for the war like and aggressive Krogan, encouraging fierce competition among the clans to accept their best warriors into the guard where they would get the best fights on some of the harshest worlds in the Galaxy.  Krogan Guard units have served with distinction on Duxn, Felucia, Quesh, Catachan, Raxus Prime, and Armaggedon.  The Krogan have gone through something of a cultural renissance as they begin to rebuild cities on Tuchanka and their population expands to meet the demands of the eager Imperial Guard.
The Quarians were late comers to war against the Reapers but have been invaluable to the Imperium during and since the conflict ended.  The Quarians had one of the largest fleets of Mass Relay jump capable ships allowing them to transport much need troops and supplies to major conflict zones.  The Imperium has provided support in return with recolonizing their home world of Rannoch and improving their weak immune systems.  
The Geth are currently the only Synthetic race that has been permitted to join the Imperium.  The Geth were created by the Quarians but rebelled against them after the Quarians tried to destroy them.  They initially fought for the Reapers but after the Battle of Rannoch became valuable allies.  The Geth mostly keep their distance from the Imperium at large, something everyone is mostly comfortable with.  The Geth refused to join the CIS sighting it as illogical.

Sangheili-
The Sangheili are a saurian species of fierce, proud, strong, and intelligent warriors native to the world of Sanghelios.  They have four manible-like lips and two hearts making them naturally physically fit. The Sangheili were one of the founding races of the Covenant and formed the back bone of its military for almost its entire existence.  
The Sangheili are divided into various nation states on their homeworld of Sanghelios these states war with eachother frequently producing a culture based on honor and merit.  The nation states were ruled by leaders known as Kaidon elected by a council of elders.  It was custom for those who disapproved of the Kaidon to attempt to assassinate the Kaidon.  If they failed the punishment was often harsh with death being frequent.
The Sangheili revered the Forerunners as gods and the objects they had left behind.  They found themselves at odds with San 'Shyuum leading to a war.  The San 'Shyuum were weaker had access to a Forerunner Keyship with which they fought the Sangheili to a bloody stand still.  They formed the Covenant to search together for the mysteries of the Forerunners an arangement that worked well though the Sangheili would develop a rivalry with the Jiralhanae.
When the Human-Covenant war began the Sangheili expected an easy victory.  Human ships and weapons were inferior to their mighty battleships and plasma weapons, they were also physically weaker than the Sangheili.  They burned many human worlds to ash with limited loses in space.
However the humans dragged the war out for twenty seven bloody years, fighting the Covenant for every world relentlessly.  The humans creativity and determination won them several critical victories and slowly the respect of many Sangheili.  Many began to wonder why the San 'Shyuum had not offered the humans membership in the Covenant.
Then the Halo event occured and the Covenant was shaken to its core.  The reputation of the Sangheili was called into question an a divide began to grow between the Sangheili and the San 'Shyuum.  The Jiralhanae were quickly moved in to fill out the Sangheili's role in the Covenant leading eventually to the Great Schism as the Sangheili broke away from the Covenant.
The Sangheili joined forces with Humanity to defeat the Covenant but found themselves embroiled in a conflict with themselves.  They had relied upon the Covenant for so long their own abilities to do basic tasks such as farming or ship matinence had fallen by the wayside.  Civil war erupted that nearly doomed the Sangheili.
The Sangheili however would recover and eventually join the Imperium as valued members.  The Sangheili's fierce warriors are highly valued in the Imperial Guard and Navy.  For the most part they have become fiercly loyal members of the Imperium who have a zero tolerance policy to traitors.

Other former Covenant races-
Other former members of the Covenant have found a place in the Imperium.  The Huragok are valued for their technical skills able to fix almost anything from a coffee maker to an Emperor Class Titan.   The Lekgolo are likewise valued for their uses in mining and war being able to eat through al sorts of materials or be used as walking tanks.  The Yanme'e took some time to aclimatize to the Imperium but soon become a highly industrious and resourceful member of the Imperium.  The Kig-Yar adjusted quickly to the Imperium serving as scouts, snipers, and privateers or as lawyers.  The Unggoy had some trouble finding a comfortable place in the Imperium, their role as cannon fodder being mostly taken by the Imperial Guard.  The Unggoy found a new role doing menial jobs for the Imperium as a source of cheap labor.

Equine-
The Equines of Equestria are an example of a race that beat the odds in a harsh galaxy to become a valued part of the Imperium.  The Equines or Ponies are sentient horse like creatures native to the planet of  Equestria.  They come in three variates; sturdy and strong Earth Ponies, winged weather manipulating Pegasus Ponies, and horned magic wielding Unicorns.
The Equines lived in relative peace for almost a thousand years, a society built upon a belief in Harmony and diplomacy.  Their society was mostly agrarian but they possessed some modest technology.  Magic was their true strength as they used it to manipulate the world around them to support themselves.  Under the watch full of the Demigoddesses Celestia and Luna, they flourished.
Then humans came, thankfully peacefully.  The OSA found the Ponies during the early days of the First Great Galactic War and established an outpost on the planet.   For years the Equines and humans lived in relative peace and harmony until the war came knocking on Equestria's door.  
The Battle of Equestria was one of the largest and most brutal battles of the war as the Iron Warriors, the Tau, and the Republic assaulted Equestria.  The Iron Warriors caused massive damage to the planets surface, bombing cities into ruin from orbit and setting its rolling plains a blaze.  The Ponies and the small OSA garrison barely held out long enough for reinforcements to arrive and drive the Iron Warriors and their Imperial Army forces from the world.
Equestria was left in ruins, its ecology destroyed, cities in ruins, and millions of civilian deaths.  Many feared that the Equine races would die out within fifty years unless dramatic change occured.
Fittingly it was the Iron Warriors who would bring that change.  After the Anaxes Accord was signed and the new Imperium formed the God Emperor commanded his son Perturabo to rebuild Equestria and heal the damage he had done.  Perturabo saw it as a chance to full fill his secret dream to build a true utopian society.  He committed the entirty of the Iron Warriors to the project and personally oversaw much of the work.  Equestria would become the flagship humanitarian aid project for the Imperium in the post war period.  
Within ten years, Equestria's biosphere was healed of much of the damage suffered in the battle.  The lush fields returned and were soon in bloom.  Perturabo rebuilt every city he had destroyed from the ground up while restoring and improving those that had survived.  Equestria was soon dotted with great cities with spires of white.  Perturabo buried the hatchet with the Equines and since then Equestria has flourished.  
The Equines proved to be quick learners and soon began adapting new concepts to their daily lives and improving upon them.  Improved farming techniques have turned Equestria into one of the most profitable agricultural centers in the Imperium, easily able to feed dozens of worlds on its own and still never have a bare pantry.  Careful mining has turned out countless precious stones which have become another major export, some as focusing crystals for Lightsabers and others as the tips of bolt gun rounds and chain sword teeth.  Some of the finest weapons and ammunition in the Imperium have a root in Equestria's mining business.
Equestria has also become a great center of learning and research boasting some of the best and largest universities, libraries, and research faciluties in the Imperium.  Much of the research is focussed towards more efficent and more effective agricultural devlopment with less enviromental impact.  Some discoveries however have lead to the development of new weapons to use against the Tyranids such as powerful pesticides.  Research into the arcane arts is also extensive on Equestria with several of the great libraries having been visited by (and having books on loan to) such individuals Jedi Grandmaster Yoda, Primarchs Perturabo, Lorgar, Sanguinus, Horus, Magnus, and Corax, and even the God Emperor himself.  
Equestria's commitments on the military front are also notable.  Equestria plays host to one of the finest Medical centers for wounded or traumatized guardsmen in the Imperium.  Equines units began appearing in the Imperial Guard shortly after Perturabo completed Equestria's reconstruction.  Initially they were meet with some confusion as to what to do with them but eventually several commanders worked out a place for them.  Equestrian Guard Regiments make excellent rapid reaction forces and support units.  Perturabo designed special battle suits that would allow Equines to fight alongside more humanoid Guardsmen with little difficulty.  He even designed modifications to various vehicles and even aircraft to support Equine opperators.  Equestrian units are also good for the morale of other Guardsmen as their up beat attitudes can make things easier in the harshest combat zones.
The Iron Warriors also ensured Equestria would be one of the most defensible worlds in the Imperium with many of the of the cities possessing some of the best void shields around.  The Cities are also designed to present as many advantages to the defenders as possible with numerous choke points where enemy movement can be crippled.   Orbital battle stations and ground to space cannons were constructed but in such a way as to not impede on Equestria's natural beauty.
The Equines themselves have adapted well to their new situation.  They are bright enough to quickly understand many complex concepts relatively quickly resulting in many scientists, doctors, and engineers.   They also serve well as diplomats, nurses, and psychological consulers partiailly due to their friendly and comforting apperance and partially out of an in born desire to help others.  They are considered up standing model citizens of the Imperium, though some Chapters of Space Marines just can't stand them.    

Others-
There are countless other minor species within the Imperium, most with little effect in the grand scheme of things.  Some are simply hostile to all outsiders and refuse to accept the strength of the Imperium.  Often times this is through violence.
One such race were the Na'vii, natives of the world of Pandora.  The Coperate forces attempted to preform mining operations on the planet only to meet with fierce resistance from the Na'vii.  Communications broke down into outright war and many troops were killed.  A debate arose whether or not to simply allow the matter to rest but in the end the value of minerals present drew the Imperium back.  What they found was a much fiercer and war like Na'vii who immeditaly attacked Imperial first Contact teams.  
It was soon discovered the Na'vii had fallen into the grip of chaos following the initial settlement and were deep in its thrall.  The Black Templars were dispatched to put the creatures out of their misery.  The Jedi order discovered several tribes that were not tainted and managed to save them, but the rest were put to the sword.  The surviving Na'vii were moved onto reservations away from the valuable mineral deposits and were allowed to continue on as they had before.