Mikaeus, the Unhallowed + Grim Poppet + Yahenni, Undying Partisan

Mikaeus, the Unhallowed

Grim Poppet

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Grim Poppet.
2. When Grim Poppet dies, its undying ability triggers, returning it from your graveyard to the battlefield without a +1/+1 counter on it due to its replacement effect.
3. Resolve the Yahenni ability
4. Repeat.

This clever loop centers around Mikaeus, the Unhallowed, whose passive anthem grants the crucial undying ability to your non-Human creatures. When you sacrifice Grim Poppet to Yahenni, Undying Partisan, the Poppet's undying ability triggers, returning it to the battlefield fresh and ready to die again because its native -1/-1 counters don't count as +1/+1 counters to prevent it. Yahenni, Undying Partisan happily grows with a +1/+1 counter on every iteration while staying safely protected behind its own sacrifice ability.