Agatha's Soul Cauldron, Walking Ballista, and Butcher Ghoul

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Walking Ballista in exile
• Butcher Ghoul on the battlefield
• Butcher Ghoul has at least one +1/+1 counter on it

Steps

1. Activate Butcher Ghoul using Walking Ballista's second ability by removing a +1/+1 counter from it
2. Repeat step 1 until Butcher Ghoul has no +1/+1 counters on it
3. Resolve all Butcher Ghoul abilities dealing 1 damage to Butcher Ghoul, and any remaining damage to any target(s)
4. Butcher Ghoul dies as a state-based action due to having 0 toughness
5. Butcher Ghoul'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