Picture this... A dungeon which is VERY DIFFICULT and requires grouping to delve very deeply inside (unbelievablky high respawn rates, difficult monsters and traps) which is fairly straightforward (not really a maze but semi linear with perhaps a few branching paths). At the bottom of this dungeon is a Crystal Ball. Now there could be several cool uses for this Crystal ball for players who reach it and are physically there but the main idea would be this, when you touch the crystal ball you get to choose a bonus for your faction (i.e. you could choose only one: +10% XP gain for  your faction/+1 to hit for your faction/-10% XP gain for a different Faction/-1 to hit for a diffrent facton)

 

So, a group of Good players could group together to fight the very difficult monsters and if they reach the crystal ball they can choose an advantage for their faction or a disadvantage for a faction of there choice (evil/neutral) which would remain in effect un til a different faction is able to reach the crystal ball... This could almost guarentee that this dungeon would be a fantastic PVP spot and would be "guarded" since it could pose an advantage.

 

The mmore cool things the Crystal Ball could do , the harder folks would fight to retain it (i.e. better drops, more intellect- Whatever you could think of)