“Mankind has never been alone amongst the stars. There have ever been the other races of the universe. It is neither in Man’s nature to share his worlds with the aliens nor in theirs to share with Man. And so there has always been conflict and war. An unending series of wars. Wars of annihilation. Wars of genocide. The alien races are an abomination. We must fight them to their last breath; no quarter asked, none given. Even the places of the alien must be abhorred and shunned. Any trace of their being must be erased from the landscape lest its foul taint blight us.”
–Inquisitor Grunwald, Ordo Xenos
The Inquisitors of the Ordo Xenos accept responsibility for protecting humanity from the predations of aliens. To most of the Imperium, the alien is an abomination, a heathen who desires humanity’s destruction and who must be slain for the good of mankind. Most Inquisitors share this view and pursue the alien to the point of extinction if they can.
Some aliens are a threat to the Imperium in a military sense, invading large swathes of Imperial space, ransacking planets and killing or enslaving the inhabitants. The green-skinned rampaging Orks and voracious Tyranids are chief among these large-scale threats. The Imperial Guard and Imperial Navy are the main weapons against these xenos hordes, and the Imperium’s war zones are constantly ablaze with battles against them. The Ordo Xenos is instrumental in leading the Imperium’s military forces against major xenos invasions, gathering intelligence and deploying troops. An Inquisitor in this position makes decisions that can cost millions of lives and must be prepared to go further than even the most hard-hearted Imperial Guard general or Navy admiral in stemming the alien tide. Some of the Ordo Xenos’ greatest Inquisitors, such as the legendary Inquisitor Kryptmann, have sacrificed entire worlds to deny them to alien forces.
Other aliens are far more subtle. These in a way are more dangerous, because the Imperium’s armed forces cannot be brought to bear against such a foe. Some aliens can control humans or otherwise hide their tracks, living among human communities and corrupting them. Alienled cults can persist for centuries, sometimes attaining great power and prestige for their members, taking advantage of the superstitious and repressive nature of many Imperial worlds to enslave hundreds of thousands of people. Inquisitors of the Ordo Xenos search for tell-tale signs of alien infiltration, often gathering groups of nearby Inquisitors to them before they move to destroy it wherever it is found. Such Inquisitors are hard-nosed investigators who must be prepared to face inhuman enemies and show no mercy to those in thrall to the alien.
A few alien threats are dormant, waiting to emerge. Many examples of fallen alien civilizations are dotted around the galaxy on dead and quarantined worlds, and not all the aliens there are completely extinct. It only takes an ill-advised mining colony or Explorator mission to awaken something ancient and slumbering. To prevent this, many Ordo Xenos Inquisitors actively investigate the relics of alien civilizations, hunting for potential dangers among cyclopean alien cities and forgotten tomb-worlds. These Inquisitors frequently work alone and, needless to say, one of the dangers they face is awakening the very alien horrors they seek to keep dormant.
While many Ordo Xenos Inquisitors believe that all aliens must be killed, this is not true for all of them. Some believe that if an alien species does not wish the Imperium harm and does not move against Imperial interests then cooperating with them is not out of the question. Some aliens possess technology that far surpasses the Imperium’s own, such as the elegant digital weapons made by the ape-like Jokaero, and trading for such technology may be to the Imperium’s benefit. Furthermore, the Imperium shares common enemies with some species, and alliances between Imperial and alien forces are sometimes a necessity. Some Ordo Xenos Inquisitors actively foster these alliances, believing that their superior knowledge of alien methods and mindsets negates the risks of collaborating with xenos. These beliefs are considered Radical among the Ordo Xenos and their adherents can be shunned or even hunted down by their brother Inquisitors. Nevertheless, the contact an Ordo Xenos Inquisitor has with alien species can impart a belief that some of them can be used, not just destroyed, by the Imperium.
As well as having the capacity to command the Imperium’s military forces, the Ordo Xenos also have access to the Ordo’s Chamber Militant---the Deathwatch Space Marines. The Deathwatch is an unusual Space Marine Chapter that draws its members from the other Chapters of the Adeptus Astartes, with Marines serving in the Deathwatch for a set period of time before returning to their original Chapters. Most Space Marine Chapters are a part of this ancient agreement, sending Space Marines with the most appropriate skills to be trained and equipped for a term of service as specialized alien hunters under the command of the Ordo Xenos. A squad of Deathwatch Space Marines is invaluable when an Inquisitor comes to exterminate an alien infestation, investigate a potentially deadly alien world or eliminate a particularly loathsome xenos creature. Some Deathwatch squads are placed at the disposal of a conclave, but most of them are appointed to the retinue of a particular Inquisitor until his mission is complete.