Agatha's Soul Cauldron + Walking Ballista + Nearheath Stalker

Agatha's Soul Cauldron

Walking Ballista

Nearheath Stalker

How it works

1. Activate Nearheath Stalker using Walking Ballista's second ability by removing a +1/+1 counter from it.
2. Repeat step 1 until Nearheath Stalker has no +1/+1 counters on it.
3. Resolve all Nearheath Stalker abilities dealing 1 damage to Nearheath Stalker, and any remaining damage to any target(s).
4. Nearheath Stalker dies as a state-based action due to having 0 toughness.
5. Nearheath Stalker's undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Repeat.

This clever loop relies on Agatha's Soul Cauldron to feed Walking Ballista's activated ping ability directly to Nearheath Stalker in your graveyard. By utilizing the Cauldron's color-fixing mana allowance and its ability to exile cards while granting counters, Nearheath Stalker inherits the power to strip away its own counters to deal damage. When those removals shrink its toughness to zero, its native undying ability steps in to return it to the battlefield fresh with a new +1/+1 counter, resetting the entire engine for infinite damage and triggers.