Agatha's Soul Cauldron, Vampire Scrivener, and Walking Ballista

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Vampire Scrivener on the battlefield
• Walking Ballista in exile

Steps

1. Activate Vampire Scrivener by using Walking Ballista's ability by removing a +1/+1 counter from it, dealing 1 damage to any target and causing you to gain 1 life due to its lifelink
2. Vampire Scrivener triggers, putting a +1/+1 counter on it
3. Repeat

Results

• Infinite damage
• Infinite lifegain triggers
• Infinite lifegain