just had an idea i don't know if its be suggested before so hear it is ;-
in random locations in most areas in positions no one would think of going add a secret doorway to a room or realm in this room hide a quest, game, boss, prize which can only be gained in this room ( bound )of course this doorway dose not show on maps in any way so a player would have to stumble in to it and once they have completed the room they cant go back in ( one time only chance ) no porting in friends so it is a solo room and a time limit added before it can be found again
make the rooms mach the level of the player so if a L10 finds it a L10 to L12 prize is given but if a L30 finds the room a L30 to L32 prize is given but the prize would need to an epic prize worth players looking for the rooms
what do you all think