Mikaeus, the Unhallowed + Barrenton Medic

Prerequisites

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Steps

1. 1Activate Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it.
2. 2Repeat step 1 until Barrenton Medic dies as a state-based action due to having zero toughness.
3. 3Barrenton Medic dies, triggering its undying ability, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
4. 4Repeat.

Effects

• Infinite creature ETB
• Infinite creature LTB
• Infinite death triggers