Mikaeus, the Unhallowed + Defiant Greatmaw + Yahenni, Undying Partisan

Mikaeus, the Unhallowed

Defiant Greatmaw

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing Defiant Greatmaw.
2. When Defiant Greatmaw dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. When Defiant Greatmaw enters the battlefield, its first ability triggers, putting two -1/-1 counters on it.
4. Defiant Greatmaw's second ability triggers, removing a -1/-1 counter from another creature you control.
5. Resolve the Yahenni ability from step 1, causing it to gain indestructible until end of turn.
6. Repeat.

This clever loop turns Mikaeus, the Unhallowed into an engine of endless rebirth, relying on his static undying grant to bring back Defiant Greatmaw every time it falls. By using Yahenni, Undying Partisan as a reliable sacrifice outlet, you send the Greatmaw straight to the graveyard, from whence it immediately returns to the battlefield carrying a +1/+1 counter. As Defiant Greatmaw enters, its own triggered ability places two -1/-1 counters upon itself, which instantly annihilates both its existing +1/+1 counter and any lingering -1/-1 baggage through state-based actions while feeding its counter-shifting trigger. This self-neutralizing cycle repeats as often as you like, generating an infinite stream of creature sacrifices, enters-the-battlefield triggers, and deaths for Yahenni to feast upon.