Astral Arena

No more than one creature can attack each combat.
No more than one creature can block each combat.
Whenever chaos ensues, Astral Arena deals 2 damage to each creature.

Akoum

Players may cast enchantment spells as though they had flash.
Whenever chaos ensues, destroy target creature that isn't enchanted.

Aretopolis

When you planeswalk to Aretopolis and at the beginning of your upkeep, put a scroll counter on Aretopolis, then you gain life equal to the number of scroll counters on it.
When Aretopolis has ten or more scroll counters on it, planeswalk.
Whenever chaos ensues, put a scroll counter on Aretopolis, then draw cards equal to the number of scroll counters on it.