Anti-Venom, Horrifying Healer, Agatha's Soul Cauldron, Deathbringer Thoctar, and Primal Vigor

Prerequisites

• Anti-Venom, Horrifying Healer on the battlefield
• Agatha's Soul Cauldron on the battlefield
• Deathbringer Thoctar in exile
• Primal Vigor on the battlefield

Steps

1. Activate Anti-Venom using Deathbringer Thoctar's ability by removing a +1/+1 counter from it, targeting itself and putting two +1/+1 counters on it due to its replacement effect and Primal Vigor
2. Activate Anti-Venom using Deathbringer Thoctar's ability by removing a +1/+1 counter from it, dealing 1 damage to any target
3. Repeat

Results

• Infinite damage
• Infinite +1/+1 counters on a creature