Walking Ballista and Vraska Infinite Damage

Step 1: Use Dark Ritual to generate .

Step 2: Use Command Tower to ensure you have access to .

Step 3: Cast Walking Ballista with enough counters to start the combo.

Step 4: Use Vraska, Swarm's Eminence's ability to generate a Deathtouch counter on Walking Ballista when a creature you control dies.

Step 5: Use Walking Ballista to deal damage to any target, sacrificing a creature to trigger Aveline de Grandpré's ability.

Step 6: As a creature dies, Vraska, Swarm's Eminence triggers, adding a counter back onto Walking Ballista.

Step 7: Repeat steps 5 and 6 for infinite damage to any target.