Mikaeus, the Unhallowed + Yahenni, Undying Partisan + Gnarlbark Elm

Mikaeus, the Unhallowed

Yahenni, Undying Partisan

Gnarlbark Elm

How it works

1. Activate Yahenni by sacrificing Gnarlbark Elm.
2. When Gnarlbark Elm 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.