Psychophobia: E2M7 The Crypt - Level 2 (Part 5/6)
6http://www.moddb.com/mods/psychophobia/downloads
Part 5 of the second-to-last map.
So that switch releases more of the Wickeds but that's not the only thing, it also opened a secret with some medicine inside and extended the path at the very beginning.
After you leave the temple or whatever that was you'll have to get back to the beginning but on your way you'll have to fight some more Hellknights and Barons. There are also 2 Archviles but they're no problem ;)
Then, when you're finally at the beginning again, you'll have to go through a hallway full of Wickeds. I have to admit that I kinda suck here but these enemies are just so annoying because they shoot fireballs which travel by the speed of light (well, almost :P) AND chase you a bit with a zig-zig like movement so these fireballs are pretty hard to avoid sometimes. To tell you the truth, they're also one of the reason why I skipped E2M6 because there were like 10 of them 5 times (so that makes like 50 of them spread through 5 rooms) and there was almost no way to avoid their attacks :(