Reveillark + Body Double + Yahenni, Undying Partisan

Reveillark

Body Double

Yahenni, Undying Partisan

How it works

1. Activate Yahenni, Undying Partisan by sacrificing Body Double.
2. When Body Double leaves the battlefield, it triggers its Reveillark ability, returning itself from your graveyard to the battlefield as a copy of Reveillark.
3. Resolve the Yahenni, Undying Partisan ability.
4. Repeat.

This elegant loop turns a graveyard into an endless engine, centered around Body Double entering as a copy of Reveillark. By using Yahenni, Undying Partisan to sacrifice that copied Reveillark, you trigger the card's printed leaves-the-battlefield ability—which in turn targets the Body Double in your graveyard, bringing it right back to the battlefield to restart the cycle. Because Yahenni, Undying Partisan's sacrifice ability is instant-speed and doesn't cost any mana, this self-sustaining loop generates an infinite number of creature deaths, enters-the-battlefield triggers, and leaves-the-battlefield triggers.