Tormageddon

Tormageddon is a daemon Erebus cooked from Tarik Torgaddon's stolen gene-seed, then poured into Sons of Horus flesh. It stood in Lupercal's Court against the Knights-Errant and later on Terra as one of the Warmaster's uglier jokes: a Mournival brother recycled into a weapon and aimed at the men who had liked him.

It killed Iacton Qruze, which was the point. The Half-heard had escaped the Vengeful Spirit once. Tormageddon was the Legion reaching back for him with Tarik's stolen future. Grael Noctua's body was the jar. The thing inside did not bother keeping Noctua's manners.

A daemon made of a friend's seed is the XVI's idea of poetry. Torgaddon died trying to keep Horus human. Tormageddon is what the court did with the leftovers. It still answers to the Warp. It does not answer to Tarik.