The Arena is usually rather static. It's just a blank generic ground/floor for the Mages to do battle on. Well, what if the Arena could do some more interesting things?
1. Unstable ground: During the Upkeep phase, zones can partially crumble away, leaving less room for corporeal objects. Zones can even disappear entirely. Don't worry, they'll come back. If a zone disappears with a mage standing on it, the Mage just moves one zone away right before it falls. Keep track of the zone-sizes using counters. (No Terrain/movement control spellbooks allowed, i.e. the Forcemaster. All cards with the "push" effect are banned.)
2. Death by Smashing!: The Arena has been lifted into the sky, and without the outer walls! The whole Arena has been enchanted so that no one can die while they are in the arena. Keyword being "in the arena". All melee attacks targeting a mage have the effect of pushing that mage 1 zone 2 zones, 3 zones, 4 zones, or 5 zones away in the direction of the attack depending on how much total damage the attacked Mage has by the end of the attack. Ranged attacks do the same thing, except they can only push a mage up to 3 zones away, also depending on how much damage the attacked Mage has total by the end of the attack. The Health stat is ignored for all Mages. If an effect says gain X life, your Mage loses X Damage instead.
If you have 3+ Damage you are pushed one zone away from the attacker in the opposite direction of the attack.
If you have 6+ Damage you are pushed 2 zones away from the attacker in the direction of the attack
And so on. Don't forget that Ranged attacks can only push an enemy Mage up to 3 zones away! Non-Mage Creatures are also pushed by attacks except they can only be pushed 1 zone away by a ranged attack and 2 zones away by a melee attack.
And of course, if you fall of the edge of the arena, you fall to your death.
Additional options: Both players have an infinite number of free action, no mana cost resurrections that you can only use on your Mage and don't exist in your spellbook. At the end of a time limit, whoever has used the most of these resurrections loses.
OR you can have a limited number of these special resurrections, but when you run out of them you lose.
(No Terrain/movement control spellbooks allowed, i.e. the Forcemaster. All cards with the "push" effect are banned. Inspired by the Super Smash bros Videogames)
3. LAVA ESCAPE!: The Mages start in the left corners of the Arena in relation to the player with first initiative (so for the player who gets initiative second, that wall is on their right). The Mages have been enchanted so that the force of gravity from the starting wall of the Arena has been amplified on them, and the force of gravity on them from the ground has been significantly nerfed. Now Mages are standing on the wall of the arena! But the lava level is rising, so you need to get your mage to "higher" ground to avoid being burned to death. All other objects in the arena have normal gravity, so they can pose as obstacles. Attacks and incantations have only a range of up to one zone "above" or "below" and up to 2 zones "forward" or "behind", in relation to the lava. Every 15 minutes of real time the lava level rises by 1 column of zones, completely destroying anything it covers. You win by either A) getting your mage to the exit on the other side of the arena before the enemy mage. The exit is now on the middle of the opposite wall of the arena. Passing through it before your enemy grants you victory. Or B) if the enemy Mage dies before you. Falling in the lava is an instant death. Corporeal walls can float on the lava but standing on a corporeal wall that deals passage attacks will cause a mage to take that attack when they first step on it.
Additionally, creatures cannot have the fast trait unless they also have the slow trait. Since the two traits cancel each other out, creatures cannot be fast.
4. Trapped in a Fish Tank (4 mage free-for-all!): All but the 4 corner zones have been completely submerged in water! All zones are now zone pillars, and are composed of 3 zonelettes, which are treated as separate zones, and rules about zones and zone movement work mostly the same way for zonelettes. However, enchantments that target a zone instead target the whole zone pillar rather than a single zonelette. Creatures cannot have flying. The 4 zone pillars that aren't completely submerged have their middle (lv1) zonelettes filled with air, and its Lv0 and Lv2 zonelettes are filled with water. Your Mage will sometimes need to enter one of these air pockets to refill their head bubble with oxygen. All non-mage creatures now have gills. Each mage can hold their breath for 3 rounds after they run out of oxygen. Each mage starts with 6 oxygen (max 6) and they lose 1 oxygen each upkeep phase while in water. If a mage is in a zonelette with air, that mage gains 2 oxygen instead. If it's too difficult to keep track of where everything is using height counters, use three boards: Lv0, Lv1 and Lv2. Don't forget that corresponding zones on different boards are in the same zone pillar i.e. the top right corner zone of all three boards are in the same zone pillar. Walls can also be cast on the border between two zones of different heights.
And that's all I've come up with for now. I haven't had the chance to test any of these variants yet, so feel free to edit the rules and banlists as you see fit. I would really like it if you posted what's worked and what hasn't for you when playing these variants. Have fun!