Colfenor, the Last Yew + Gutter Grime + Goblin Bombardment

Colfenor, the Last Yew

Gutter Grime

Goblin Bombardment

How it works

1. Cast the creature card in your hand by paying 0.
2. Either that creature dies as a state-based action due to having zero toughness, or activate Goblin Bombardment by sacrificing that creature.
3. Gutter Grime triggers, putting a slime counter on it and creating a X/X Ooze creature token.
4. Activate Goblin Bombardment by sacrificing the Ooze.
5. When the Ooze dies, Colfenor triggers, returning the creature card from your graveyard to your hand.
6. Resolve the Goblin Bombardment abilities, dealing 1 damage each time.
7. Repeat.

This loop relies on the constant recycling of a zero-toughness creature to fuel Goblin Bombardment for endless damage and sacrifice triggers. As your creatures perish, Gutter Grime scales up by stacking slime counters and spawning ever-larger Ooze tokens, which in turn feed the Bombardment. When those growing Oozes eventually die, Colfenor, the Last Yew steps in to leverage their greater toughness and fish your original creature card right back out of the graveyard to hand, letting you repeat the entire cycle indefinitely.