Felidar Guardian + Vesperlark + Yahenni, Undying Partisan

Felidar Guardian

Vesperlark

Yahenni, Undying Partisan

How it works

1. Cast Felidar Guardian by paying 3.
2. When Felidar Guardian enters the battlefield, it triggers, targeting Vesperlark.
3. Holding priority, activate Yahenni by sacrificing Felidar Guardian.
4. Resolve the Felidar Guardian trigger, blinking Vesperlark.
5. When Vesperlark leaves the battlefield, it triggers, returning Felidar Guardian from your graveyard to the battlefield.
6. Repeat from step 2.

This loop works by leveraging a continuous sacrifice and recursion cycle to generate infinite triggers. By casting Felidar Guardian, you trigger its ability to blink another permanent, but instead of letting it resolve normally, you immediately use Yahenni, Undying Partisan to sacrifice the Guardian. This death forces Vesperlark to leave the battlefield, triggering its ability to pull Felidar Guardian right back out of your graveyard and back onto the battlefield to restart the process.