Mikaeus, the Unhallowed + Phyrexian Altar + Gravelgill Axeshark

Mikaeus, the Unhallowed

Phyrexian Altar

Gravelgill Axeshark

How it works

1. Activate Phyrexian Altar by sacrificing Gravelgill Axeshark.
2. When Gravelgill Axeshark 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 Gravelgill Axeshark.
4. When Gravelgill Axeshark 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 relies on the brilliant counter-balancing act between Mikaeus, the Unhallowed and Gravelgill Axeshark. Because Mikaeus grants undying while Gravelgill Axeshark naturally features persist, the creature can alternate between returning with a +1/+1 counter and a -1/-1 counter, which immediately cancel each other out as a state-based action and leave the shark fresh for the next cycle. Sacrificing it repeatedly to Phyrexian Altar not only converts this endless cycle into an unlimited supply of colored mana, but also triggers infinite entry, exit, and death events to fuel whatever win condition your heart desires.