Geralf, the Fleshwright + Putrid Goblin + Yahenni, Undying Partisan

Geralf, the Fleshwright

Putrid Goblin

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Putrid Goblin.
2. When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Putrid Goblin enters the battlefield, Geralf's second ability triggers, putting a number of +1/+1 counters on it equal to the number of other Zombies that entered the battlefield under your cotnrol this turn.
4. Resolve the Yahenni ability, giving it indestructible until end of turn.
5. Repeat.

This loop is built on the elegant interaction between Putrid Goblin and Yahenni, Undying Partisan, where Yahenni's free sacrifice outlet endlessly feeds on the Goblin's persist ability to trigger dying and entering-the-battlefield events over and over. Because persist returns the Goblin with a -1/-1 counter, Geralf, the Fleshwright steps in as the crucial catalyst: whenever the Zombie enters the battlefield, Geralf's second ability places +1/+1 counters on it based on previous entries, which immediately cancel out the -1/-1 counter via state-based actions. This resets the Goblin's persist ability so it can be sacrificed to Yahenni indefinitely, generating infinite +1/+1 counters on your creatures alongside boundless sacrifices and triggers.