40K3 conversion by Tom and Erik Setzer; Based on 40K2 background and rules by Mike Freeman
This was taken from White Dwarf 193, where the Cullexus was mentioned in the Eversor article. I made up the rest.
Assassins are one of the Imperium's greatest weapons for defeating undermining Planetary Governors and rogue psykers. Instead of sending regiments of Imperial Guard and Space Marines to stop such a threat, a swift blow from an assassin tends to rip the center from any rebellion. Rebel forces often lack the stomach for fighting when their leader is discovered beheaded and heartless in his chamber. Assassins are recruited from orphanages, young humans with no family and no name. They are taken to a specific temple, where they learn a certain way of fighting. For instance, the Eversor Assassin uses scare tactics, and the Vindicare Assassin is used as a sniper. All assassins are deadly in their own aspect, and as a whole. If one of these orphans shows some form of latent psychic ability, they are taken to the Cullexus temple. Here they learn the art of combat, and learn to use their psychic powers to defend themselves and terrorize the Emperor's foes. They are used mostly to take care of rogue pyskers, as even at the height of their Chaos powers, they cannot rival the mastery of the Cullexus. They use the Emperor to terrorize foes, and they are said to channel his rage through them form the Warp.
Weapons: Cullexus Force Weapons, needle pistol (counts as needle sniper rifle with 12" range and type Pistol), power sword. The Cullexus also has a special Psychic Hood and a Cameoline Cloak.
Hail of Fire
Daemonic Resistance-The Cullexus is trained on how to avoid daemons at a very early age. He may re-roll any 2's or 12's rolled while trying to use a Psychic Power.
Cullexus Force Weapon
Cullexus Psychic Powers
The Cullexus summons up frightening images of the Emperor around him, making his foes think that the Emperor is coming for them next! A single enemy unit within 6" must take a Ld test on 3d6. If they fail, they must fall back immediately.