Vespasian

Vespasian was a Lord Commander of the Emperor's Children, the one who still talked as if the Palatine Phoenix might listen. He told Fulgrim the Legion was sick. The Laer blade was the answer. Eidolon kept the other lord commander's share of the vanity; Vespasian kept the conscience, which in that Legion was a terminal condition.

He had been the counterweight to Eidolon's cruelty, a duellist and administrator who thought perfection included not murdering your own. Fulgrim heard the warning as an insult and put the daemon-sword through the man who had loved him enough to say it.

The Third Legion did not replace him. It did not want that office filled. Chemos remembers a lord commander only as a name on a list of the purged. Vespasian died trying to treat a primarch as a brother. The Laer sword has never needed a second argument.