Samus

Samus is a daemon of the Ruinstorm, not a Space Marine: the voice that says it is the man beside you. It first wore Luna Wolf flesh in the Whisperheads, then a Word Bearer on Calth, then the Phalanx itself when Mersadie Oliton's warp-eye opened a door in Dorn's house. The chant is the weapon. The body is rented.

Ventanus stabbed it with an athame. Dorn killed it and watched it stand up in a new corpse. Oliton closed the gate with her own death. Loken later cut another shell apart on the Vengeful Spirit while someone on Terra read the name aloud like a ward. Samus does not stay dead. That is the thesis.

The Warp claims the daemon was born from Loken's murder, which is the kind of chronology only the Empyrean finds tidy. The Great Crusade heard the footsteps first. The Siege heard them last. The voice is still looking for a throat.