the quest Razor Blade smile requires you to beat vicous Halls of Steel with 3 classes. I'm pretty sure i've said this 3-4 times up to now.
Step one: Beat HARD Halls of Steel with 4 classes (I did it with Monk, Wizard, Thief and Paladin). This unlocks a new dungeon a little to the left of HARD Halls of Steel. It is called "Halls of Steel" and it's difficulty is VICIOUS, as opposed to the regular Halls of Steel, which is labeled HARD. This is how you know which is which without entering.
EDIT: Step One point Five (1.5) You enter the new dungeon and upon seeing vicious animated armors, Illusions, resist lowering golems, 50 Death Protections on a fat Indomitable and 1400 HP on a fat BlahBlah, and find no 50% magic resist thingy, you go "Awwww, cmon', this is beyond insane", and proceede to beat it effortlessly with a Monk.
Step two: You beat the same dungeon, the VICIOUS one, with 2 more classes, and you unlock the Vampire.
Step three: You come back here and tell me how in the world did you manage to do it, and you post a pic, and I tell you in all honesty that you are a much better player of this game than me and I feel very gratefull that you thaught me how to beat the only dungeon in the game that I couldn't beat with anything but the Monk. Unless it involves the Bloodmage and the Warlord, or unlocking gods besides TT and GG, but I'd still be gratefull for the info.
Sorry for the tone, Unity crashes and humorous game developers got me sarcastic.