Mirrored Depths
Plane -- Karsus
Whenever a player casts a spell, that player flips a coin. If the player loses the flip, counter that spell.
Whenever chaos ensues, target player reveals the top card of their library. If it's a nonland card, you may cast it without paying its mana cost.
Planar Chaos
{2}{R}
Enchantment
At the beginning of your upkeep, flip a coin. If you lose the flip, sacrifice ~this~.
Whenever a player casts a spell, that player flips a coin. If they lose the flip, counter that spell.