Polernarv

Polernarv is a demon whose goal is the death of Cairo Brand and the consumption of his soul. When Cairo hunted down and captured the demon lord responsible for the tiefling's own lineage, he killed many servants and soldiers of that demon lord - including Polernarv's mother and compatriots. To repay the mortal for his list of grievous offences, he searched for Cairo - and that is when he met the party outside the Iron Tower.

He made it halfway up the tower, accepting a brawl with two creatures who both looked like Cairo, only to be wrestled down. When the party jumped in to assist, he and the Cairo-lookalike both disappeared. Since then, his whereabouts have been unknown.