Dio Promus

Dio Promus was Chief Librarian of the Ultramarines, a Macragge psyker who voted with the Librarius at Nikaea and then accepted Malcador's black when the edict made that vote a crime. He became a Knight-Errant because the Imperium still needed witches it could point at other witches.

He worked the Titan-project purges, hunting the psykers the Sigillite did not want left alive in the Emperor's basement. The war brought him back to Nikaea anyway. Svafnir Rackwulf killed him there, a Space Wolf ending a debate the Council had already lost.

Lemuel Gaumon took the name afterwards, which is how Malcador's people keep a dead man's work moving. Promus did not survive his second visit to that world. The title did. The Ultramarines were not asked for an opinion on the loan.