[quote=Leon5431]
I picture the Underhaven as something like Tyrael's man cave or something. Kind like Mar's room...except its a literal cave....talk about a low maintenance gal.
[/quote]

Actually it's more like Lucilia's cave, Tyrael just goes there because his demons do. Underhaven is suppose to be a sanctuary for Vampires, demons, and other creatures of ill intent who have no desire to continue doing evil, but also need to still live off the rewards of their evil. You know, like if vampires need blood, Underhaven provides. Demons are hungry for the flesh of mortals, they got that too. Bored and need some money, and Underhaven has some assassination contracts. It also serves as a conventional tavern for those who aren't into the whole "Eats people" aspect.