Mikaeus, the Unhallowed + Cauldron of Souls + Intruder Alarm + Animate Artifact + Phyrexian Altar

Mikaeus, the Unhallowed

Cauldron of Souls

Intruder Alarm

Animate Artifact

Phyrexian Altar

How it works

1. Activate Phyrexian Altar by sacrificing the additional nontoken non-Human creature, adding one mana of any color.
2. When the creature dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. When the creature enters the battlefield, Intruder Alarm triggers, untapping all creatures.
4. Activate Cauldron of Souls by tapping it, giving the creature persist until end of turn.
5. Activate Phyrexian Altar by sacrificing the creature, adding one mana of any color.
6. When the creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
7. When the creature enters the battlefield, Intruder Alarm triggers, untapping all creatures.
8. Repeat.

By enchanting Cauldron of Souls with Animate Artifact, we transform the Cauldron into an active creature itself, allowing it to join the engine. Mikaeus, the Unhallowed provides the critical foundation here by granting all other non-Human creatures undying, ensuring they return to the battlefield with a +1/+1 counter whenever they perish. Meanwhile, the Cauldron steps in to grant them persist, creating a perpetual counter-cancellation loop when alternated with Mikaeus's blessing. Phyrexian Altar acts as the designated executioner, converting each sacrifice into raw mana to fuel the loop. Finally, Intruder Alarm watches the chaos unfold, automatically untapping the Cauldron—and your entire board—every single time a creature enters the battlefield, making the cycle fully self-sustaining.