An arena is a location where a battle is fought. Recent events have had arenas with special rules - the "green" event had extra green tiles dropping while the 1v1 duel event had no team-up tiles. Other events are limited to characters in certain classes, this too could fall under the umbrella of an arena rule. I'm suggesting two things, first is to have regular events held in special arenas. This would, I hope, lead to interesting match-ups with new team combinations. The second is the idea that every battle is fought in a particular arena (is "venue" a better word?) with its own rules and that there should be uniform way of specifying those rules going into every battle (even if the majority of battles may be fought with 'no special rules').

Among the ideas for arena rules would be:
* Arena limited to characters in certain groups or that require a certain character.
* Tiles of a particular color might:
     - be more common or absent
     - do double damage or special effects like stun/heal/airborne/invisibility when matched
* No stunning allowed or no team-up powers allowed.

Note how some (most?) of these suggestions are already special rules that are already often implemented without the unifying concept of the arena.

There could be some special box in the opening battle opponent's screen specifying the arena rules for the upcoming battle.

I am suggestion more events that feature new, special rules; but events where the rules change in every battle should be avoided due to the confusion and effort that might cause.

A node in Deadpool's Daily that has a special arena each day might be fun.