I'm interested on what Vicious dungeons people enjoy the most, so please vote and post a list if you have the time!
Here's my ranking:
1. Demonic Library (Overall fun concept, unique, and no way to win every time. Requires varied strategies.)
2. Namtar's Lair (God this dungeon is hellish, but awesome)
3. Naga City (Interesting, as it cuts you off before any bosses, therefore it makes you think up interesting strats)
4. Dragon Isles (A serious pain to level up in, with the awful enemy set. Get's REALLY annoying after awhile)
5. Vicious Halls of Steel (Unless they add Vicious versions to Shifting Passages, Ick Swamp, and The Labyrinth, this dungeon sticks out like a sore thumb. Not unique, and there is no extra reward.)
6. Vicious Gaan-Telet (Fun at first, but I'm sick of going through 9 floors only to be thwarted by AA's doing 238 damage. And it takes an hour just to get there.)