Agatha's Soul Cauldron + Triskelion + Strangleroot Geist

Agatha's Soul Cauldron

Triskelion

Strangleroot Geist

How it works

1. Activate Strangleroot Geist using Triskelion's ability by removing a +1/+1 counter from it.
2. Repeat step 1 until Strangleroot Geist has no +1/+1 counters on it.
3. Resolve all Strangleroot Geist abilities dealing 1 damage to Strangleroot Geist, and any remaining damage to any target(s).
4. Strangleroot Geist dies as a state-based action due to having 0 toughness.
5. Strangleroot Geist's undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Repeat.

This clever loop centers on Agatha's Soul Cauldron, which allows you to exile Triskelion and grant its activated ability to any of your creatures bearing a +1/+1 counter. With this newfound power, Strangleroot Geist can repeatedly shoot itself by removing its own counters, leveraging its haste and natural resilience. When the Geist finally perishes, its undying ability brings it right back to the battlefield with a fresh +1/+1 counter ready to restart the cycle.