Agatha's Soul Cauldron, Triskelion, and Strangleroot Geist

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Triskelion in exile
• Strangleroot Geist on the battlefield
• Strangleroot Geist has at least one +1/+1 counter on it

Steps

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

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB