Bringing back different types of keys for different sorts of locks. This is not the old random key shapes and random lock shapes system; the discussion concluded that special keys should be used for a few specific purposes: game progression, a one time use reward, or some non-unique type of door where each key is one-time use or limited use. In particular, this third one could be used in Gehennom to block off areas, with “soul keys” or something similar that open special doors there and are generated with demons. Gehennom doors could also involve a blood ritual requiring some sort of expenditure of resources or damage to the player.