Add a time limit and we have a winner here. Like 15 minutes in a room full of supplies, you have to enter without armour, empty inventory, etc. You need a group of max 5~ people. So basically, you have 15 minutes to prepare before the boss comes and kicks the crap out of you. Maybe different bosses, like a range/mage/melee boss, and as the time goes on, you are given hints about which boss it'll be. It'd involve high non-combats, combats, and strategy. Thats another excellent idea. Maybe a room full of walls, like a maze, and the walls move from time to time, so lets say you have a tanker, 2 guys meleeing the boss, and 5 guys ranging/maging, then the walls move and now your rangers/mages have a nice wall in front of them and the meleers are getting owned, so the rangers/mages have to find a way to get in range with the beast again quickly. You could add restrictions, like the boss is using protect from melee all the time, and doing high damage to all opponents nearby, so you HAVE to range it. Or the boss attacks push you away from him, and he uses protect from range and has high magic defence, so you have to get in melee range to kill him. InsanityV2 and Promise have a point: its not always about the boss himself, but the enviroment.