Activate Walking Ballista by removing a +1/+1 counter on it, targeting itself, but putting two +1/+1 counters on it due to Vigor.
Activate Walking Ballista by removing a +1/+1 counter on it, dealing 1 damage to any target.
Repeat.

Infinite damage

Infinite +1/+1 counters on creatures you control

Vigor

Corpsejack Menace

Walking Ballista

Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to itself.
Rite of Passage triggers, putting two +1/+1 counters on Walking Ballista.
Repeat an arbitrarily large number of times.
Move to the next turn, removing all damage marked on Walking Ballista.
Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to any target.
Repeat step 5 as desired.

Rite of Passage

Cast Gatta and Luzzu by paying {2}{W}.
When Gatta and Luzzu enters the battlefield, it triggers, targeting Walking Ballista.
Activate Walking Ballista by removing a +1/+1 counter from it, targeting itself, but instead putting two +1/+1 counters on it due to Gatta and Luzzu and Corpsejack Menace.
Activate Walking Ballista by removing a +1/+1 counter from it, dealing 1 damage to any target.
Repeat from step 3.

Infinite +1/+1 counters on a creature

Gatta and Luzzu

Activate Anti-Venom using Walking Ballista'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 Corpsejack Menace.
Activate Anti-Venom using Walking Ballista's ability by removing a +1/+1 counter from it, dealing 1 damage to any target.
Repeat.

Anti-Venom, Horrifying Healer

Agatha's Soul Cauldron

Activate Grimgrin by sacrificing Walking Archive.
When Walking Archive dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to its replacement effect.
Resolve the Grimgrin ability.
Repeat.

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Infinite death triggers

Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight

Grimgrin, Corpse-Born

Walking Archive

Cast Illicit Masquerade by paying {3}{B}. When it enters, its first ability triggers, putting an impostor counter on Skullbriar.
Cast Perigee Beckoner for its warp cost by paying {1}{B}.
When Perigee Beckoner enters, it triggers, targeting Skullbriar.
Activate Grimgrin by sacrificing Perigee Beckoner.
Activate Grimgrin by sacrificing Skullbriar.
When Skullbriar dies, Illicit Masquerade's second ability and Skullbriar's ability granted to it by Perigee Beckoner trigger.
Resolve the Skullbriar trigger, returning it from your graveyard to the battlefield.
Resolve the Illicit Masquerade trigger, failing to exile Skullbriar as it has left your graveyard and returning Perigee Beckoner from your graveyard to the battlefield.
Resolve the Grimgrin ability from step 5.
Repeat from step 3.

Skullbriar, the Walking Grave

Illicit Masquerade

Perigee Beckoner

Activate Grimgrin by sacrificing Forsaken Miner.
If able, activate Crystalline Crawler's first ability by removing a +1/+1 counter from it, adding {B}.
Activate Walking Ballista by removing a +1/+1 counter from it, targeting an opponent or a permanent an opponent controls.
When you commit that crime, Forsaken Miner triggers, causing you to pay {B} to return Forsaken Miner from your graveyard to the battlefield.
When Forsaken Miner enters the battlefield, Celes's second ability triggers, putting a +1/+1 counter on each creature you control.
Resolve the Walking Ballista ability from step 3.
Repeat.

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