Captain Idaeus

Idaeus was Captain of the Ultramarines Fourth, the unorthodox officer who taught Uriel Ventris that the Codex is a floor, not a ceiling, and then died on Thracia proving the lesson. He left Ventris the power sword and the company. Ventris has been arguing with both ever since.

The Fourth took Idaeus's habit of thinking past the page into Pavonis and a dozen later wars. The Chapter still files him as a hero who bent doctrine without breaking faith. That is a narrower path than it sounds. Most captains who try it become a caution. Idaeus became a standard.

Macragge raised him. Thracia kept him. The sword Ventris carries is the part of Idaeus that still issues orders. The rest is a grave the Fourth salutes and then has to live up to.