Colfenor, the Last Yew + Gutter Grime + Phyrexian Altar

Colfenor, the Last Yew

Gutter Grime

Phyrexian Altar

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 Phyrexian Altar by sacrificing that creature, adding one mana of any color.
3. Gutter Grime triggers, putting a slime counter on it and creating a X/X Ooze creature token.
4. Activate Phyrexian Altar by sacrificing the Ooze, adding one mana of any color.
5. When the Ooze dies, Colfenor triggers, returning the creature card from your graveyard to your hand.
6. Repeat.

This loop leverages Colfenor, the Last Yew as a recursive bridge, letting you continuously recycle a creature with zero toughness or one you immediately sacrifice to Phyrexian Altar for colored mana. Every time your sacrificed creatures hit the graveyard, Gutter Grime steps in to build an ever-growing army of Ooze tokens fueled by the accumulating slime counters. Because those Oozes have lesser toughness than your recycled threats, sacrificing them back to Phyrexian Altar triggers Colfenor, the Last Yew once again to return your original creature straight to your hand—keeping the entire engine running infinitely.