Infinite Damage with Walking Ballista and Vraska

Step 1: Have Vraska, Swarm's Eminence and Hooded Blightfang on the battlefield.

Step 2: Cast Walking Ballista with at least one +1/+1 counter.

Step 3: Cast or activate Ghave, Guru of Spores to add a +1/+1 counter to Walking Ballista.

Step 4: Remove a +1/+1 counter from Walking Ballista to deal 1 damage to any target. With Vraska, Walking Ballista has deathtouch.

Step 5: Hooded Blightfang triggers, draining 1 life from each opponent.

Step 6: Use the effect of Ghave, Guru of Spores to replace the counter on Walking Ballista.

Repeat Steps 4-6 for infinite damage and life drain.