Lemartes

Lemartes is Guardian of the Lost, the Blood Angels Chaplain who fell into the Black Rage and then refused to stay there. He leads the Death Company from inside the vision, which is supposed to be impossible and is therefore why Dante still signs the orders.

Most brothers who hear Sanguinius die do not come back with a crozius still in hand. Lemartes did, and the Chapter built a title around the accident. He is both patient and weapon, which is an uncomfortable combination even on Baal, where uncomfortable combinations are the local industry.

The Lost follow him because he is already where they are going. That is the mercy. It is also the threat.