Mikaeus, the Unhallowed + Phyrexian Altar + Lesser Masticore

Mikaeus, the Unhallowed

Phyrexian Altar

Lesser Masticore

How it works

1. Activate Phyrexian Altar by sacrificing Lesser Masticore.
2. When Lesser Masticore dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Activate Phyrexian Altar by sacrificing Lesser Masticore.
4. When Lesser Masticore dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
5. Repeat.

This clever loop exploits a fascinating rules interaction between two opposing mechanics: persist and undying. Because Lesser Masticore enters with a -1/-1 counter from its own persist ability, it dies without any +1/+1 counters, allowing Mikaeus, the Unhallowed's static lord ability to grant it undying for its next death; conversely, when it returns via undying with a +1/+1 counter, that counter immediately annihilates the -1/-1 counter as a state-based action, resetting the Masticore so persist can trigger again on the following cycle. Phyrexian Altar acts as the engine that both fuels this endless cycle through its sacrifice outlet and converts the repeating deaths into an infinite supply of any color of mana.