It would be nice to have a world that locates yourself into a Lava Castle. With enemies like demons and stuff like that to fight. For currency and weapons. The boss would be the devil himself, dropping certain items (maybe potions, weapons, new skills?) for the player to obtain.
The castle would king of look like Bowsers castle from Mario. Lava would surround the castle, fights upon fights ranging from different enemies. Quests would be killing the demons for a special item, or spell.
Please let me know about what you think, I think it would be a fun location to play at and enjoyable level that can be added to the game.