(Usually Non-Player Characters)
Vicous and Unfriendly. Raptileons have been fighting the Imperium for about a 7600 years, using guerilla warfare tactics.
(A race briefly discussed in both Xenology and The Radical's Handbook, but only through the description of their equipment.)
A little known of race from the galactic north, the Xenarch are most imfamous for their use in direct energy based technology, capable of producing bolts of electricity that arch towards their target. Warp-worshipping isolationalists, the Xenarchs do not interact with the Imperium or most other races often, a fact helped by their distance from other known Empires as well as being outside the reach of the Astronomicon makes trade with them extremely rare and limited with the Imperium to a very few brave (or foolhardy) Rogue Traders.
Aside from direct energy weapons the Xenarch utilize biotics (a noteable example being one gathered by Inquisitor Ralei which still had the user's eyeball attached to it) and are designed to harness and enhance the natural bio-electrical energies of the host body to function.
Rules for the Xenarch Death-Arc can be found in The Radical's Handbook.
Ancients enemies of man. The Fusion have arisen to reclaim the Galaxy from the Imperium of Man.