Colfenor, the Last Yew + Gutter Grime + Yahenni, Undying Partisan

Colfenor, the Last Yew

Gutter Grime

Yahenni, Undying Partisan

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 Yahenni by sacrificing that creature.
3. Gutter Grime triggers, putting a slime counter on it and creating a X/X Ooze creature token.
4. Activate Yahenni by sacrificing the Ooze.
5. When the Ooze dies, Colfenor triggers, returning the creature card from your graveyard to your hand.
6. Resolve the Yahenni abilities, giving Yahenni indestructible until end of turn.
7. Repeat.

This intricate loop revolves around Colfenor, the Last Yew, whose death-trigger leverages toughness to pull a previously sacrificed creature card right back from your graveyard to your hand. As creatures enter and perish, Gutter Grime scales up with slime counters to continually manufacture larger and larger Ooze tokens, which serve as the vital fodder needed to keep the engine moving. Meanwhile, Yahenni, Undying Partisan acts as the active sacrifice outlet that fuels the sequence while growing steadily more massive with every fallen opponent's creature, successfully yielding infinite death triggers, token generation, and storm count.