Q u o t e: special keys could drop and trigger quests once the player right-clicks it or speaks to an NPC about it. The quest could involve anything, of course - escorting, dungeon crawling, go kill X-monster - the reward for which is a map to a randomly-spawned chest that is only visible to the player/party completing the quest and can only be opened with the special key.
Yeah, but I have a problem with this, why not have the NPC just give you the reward instead of a map for the chest? And either the chest spawns on the same area of the key at the same time and you do have to backtrack or it will be extremely difficult to make it work, for instance the chest spawning on a previously visited place (which makes it awkward a chest appearing from nothing) and you do have to backtrack, or in an unknown area which has to be randomized at that point with the chest and not when you get there (and it can even be for some time if you cannot take down the mobs on the zone).
All in all it seems a convoluted system.
Q u o t e: On the wind a shout
The barbarian strikes down
Flesh renders from bone