Vraska, Swarm's Eminence, and Walking Ballista

Prerequisites

• Vraska, Swarm's Eminence on the battlefield
• Walking Ballista on the battlefield
• Walking Ballista has at least two +1/+1 counters
• You have a way to give Walking Ballista deathtouch

Steps

1. Give Walking Ballista deathtouch
2. Activate Walking Ballista's second ability by removing a +1/+1 counter from it, dealing 1 damage to an opponent
3. Vraska triggers, putting a +1/+1 counter on Walking Ballista
4. Repeat steps 2-3

Results

• Infinite damage