What are greater vaults?
Greater vaults are huge rooms (about 60×20), with outside walls of impenetrable rock except for a couple of granite walls in the corners. They are filled with all different kinds of out-of-depth monsters, with excellent treasure (often more than 1 artifact), and some really out-of-depth monsters. Taking on a greater vault is amazingly dangerous unless you have some speed, lots of resistances, and a teleport away spell/wand/rod.
