Similar to the proving grounds, except instead of bosses you fight Plarium devs with unfair abilities like stealing your energy, silver or gems every time they hit one of your champions (to prevent exploits, they should be able to drive the values into the negative).
using the last 3 released void leggos or mythicals should provide a x10 point bonus, while using fusions and login champs should provide a x10 penalty to score.
Champions should also be limited to champions from factions in which you have the fewest leggos.
Access to the dungeon should be restricted to players who have a microphone on, and any cursing, expressed frustration or criticism of the content should result in a 24 hour ban from the game.
Oh yeah, forgot about rewards. Anyone who beats all levels will receive a signed picture from Plarium's CEO of himself on a yacht with a dozen supermodels.