Deviously warned! Spoilers!
Gaunt's ghosts stuff, this can be found in Honour Guard and Sabbat Martyr. Ok, a Chaos cult devil! This Infardi (pilgrim) is the leader of the host that besiege the shrine world of Hagia and almost overrun it in the end. It was thought that this bastard didn't survive the final battle, but a shocking come back in Sabbat Martyr prove this wrong.
He is a very tough bastard, wearing green silk cloak and with his whole body tattooed, along with his godlike messiah-nic voice that can corrupt the souls of the weak and a strong built body that can smash people like a cat pouncing on a lil' hamster. ^^
He played a great part in making a lot of the Ghosts characters died off, mainly corrupting Cuu's psychotic mind and using him to kill his comrades inclusing Corbec (spoilers!) and also, he is one of the Nine coming to kill the saint on Herodor.