Board Thread:Warhammer 40k General Discussion/@comment-6078851-20140323165610/@comment-86.152.255.161-20140325211008

The powers of the warp said they first sought out the Khan, then Magnus and only settling for Horus seing his arrogance as a way to trap him, and they even needed Lorgar and his stooge Erebus to do it.

I personally think the powers wouldn't have let him die, they simply would have ressurected him. They were pretty determined to use someone as a pawn and he fit the bill nicely playing the figure head and tactician. Remember that it was one of the rare times the powers worked together. its probably why the Emperor destroyed his soul completely so they couldn't bring him back.