So, playing IWD EE for yet another time but you lack an evil cleric option? Looking for some Tiax-like portion of insanity? It looks like T'viy is your man.
The mod adds a brand new, one-weekend companion to Icewind Dale: Enhanced Edition. His name is T'viy. He's a chaotic evil gnome, a little bit insane follower of Urdlen, The Crawler Below. This mod is more like a weekend project, so while he has dialogues with the PC, the friendship path is shorter than that of most other IWD NPCs. However, it's still an option for all those teams that need an evil cleric... and some insanity.