Agatha's Soul Cauldron + Triskelion + Pyreheart Wolf

Agatha's Soul Cauldron

Triskelion

Pyreheart Wolf

How it works

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

This engine turns Agatha's Soul Cauldron into a lethal weapon by feeding it the activated ability of Triskelion, granting that power to any creature you control with a +1/+1 counter—including Pyreheart Wolf itself once it's on the field. By using Pyreheart Wolf's own body as the target to strip away its counters and deal damage to it, you can repeatedly reduce its toughness to zero and send it to the graveyard. Each time it dies, Pyreheart Wolf's undying ability triggers to bring it right back to the battlefield with a fresh +1/+1 counter ready to fuel the loop all over again.