Havi, the All-Father + Gerrard, Weatherlight Hero + Yahenni, Undying Partisan

Havi, the All-Father

Gerrard, Weatherlight Hero

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Gerrard.
2. When Gerrard dies, it and Havi trigger.
3. Resolve the Havi trigger, returning up to one legendary creature card with mana value 3 or less from your graveyard to the battlefield.
4. Holding priority, activate Yahenni by sacrificing Havi.
5. When Havi dies, it triggers, returning Gerrard from your graveyard to the battlefield.
6. Resolve the Gerrard trigger from step 2, failing to exile it as it is no longer in your graveyard and returning Havi from your graveyard to the battlefield.
7. Resolve the Yahenni abilities from step 1 and 4.
8. Repeat.