Devil's Catacomb
Dungeon · monsters level 79 to 86 · 2048 x 2048 m
Six floors under the temple, ending with Charon and then Azrael. Each floor is locked behind something the last one gives up - a soul crystal key, the right Metin stone, a grimace totem.
Getting there
Talk to the Catacomb Guard at Hwang Temple. You must be level 75, have beaten the Death Reaper on the ninth floor of the Demon Tower, and be in a group.