What was that wad called?

You start off in this rocky area and have to jump across these floating rock platforms across this huge pit of lava to get to this huge castle. The whole thing is heavily scripted and I believe the imps were modified and there was lightning and thunder every so often when you were outside. The end boss was some sort of big flying bat or something too. Anybody remember the name of the wad? I'm pretty sure it's at least a couple years old.

Hell's Twisted Influence? 1 or 2?

Hey that's it! Thanks a lot.