Cthulhu, Mind Warp

Stirs in It's slumber — Whenever a player draws
their second card in a turn, if Cthulhu is in the command zone, they get a madness counter.
Each opponent's maximum hand size is reduced
by three.
Whenever an opponent casts a spell that targets a permanent, if they have five or more madness counters, they flip a coin. If they win, the spell resolves normally. If they lose, you may
change the target of that spell.