Jalen

Jalen was an Alpha Legion psyker who fought the Tallarn war under a serf's cover, a Terran operative who used Argonis's orbit and the Black Oculus the way other men use a staff code. He was not Raven Guard. He only needed people to think in those categories while he worked.

The desert campaign was a harvest of secrets: who commanded, who could be turned, which Imperial Army staffer might open a gate without noticing. Jalen's gift was to stand in a room as furniture until the room said something useful, then leave the furniture behind.

After the Oculus and the serf's mask, the XX Legion stopped writing him down. Tallarn had been used. Terra had produced him. Whether he died in the dust or walked off wearing another name is the usual Alpha Legion afterword: no afterword.