Sheehan’s Funhouse

Whenever you tap this land for mana, put a -1/-1 counter on each creature with Decay.
{t}: add {b}
{b}{t}, Tap an untapped creature you control: Put
a -1/-1 counter on target creature, that creature
gain Decay (Creatures with Decay get a -1/-1
counter at the beginning of their controller's upkeep
unless they're paying 1 life.)