Exhume + Naru Meha, Master Wizard + Yahenni, Undying Partisan

Exhume

Naru Meha, Master Wizard

Yahenni, Undying Partisan

How it works

1. Cast Exhume by paying its mana cost
2. Holding priority, cast Naru Meha by paying its mana cost.
3. When Naru Meha enters, it triggers, targeting Exhume.
4. Holding priority, activate Yahenni by sacrificing Naru Meha.
5. Resolve the Naru Meha trigger, copying Exhume
6. Resolve the Exhume copy, returning Naru Meha from your graveyard to the battlefield.
7. Repeat from step 3.

This ingenious loop starts by casting Exhume to pull Naru Meha, Master Wizard from your graveyard onto the battlefield, letting her enter-the-battlefield ability target the very same Exhume on the stack. Before that copy resolves, you use Yahenni, Undying Partisan to feed Naru Meha to the graveyard as a sacrifice, which conveniently grows Yahenni with a +1/+1 counter while keeping the sacrifice outlet fueled for repetition. When the copied Exhume resolves, it brings Naru Meha right back to the battlefield to copy Exhume all over again, generating an endless cycle of creature deaths, enters-the-battlefield triggers, and graveyard returns.