Agatha's Soul Cauldron + Walking Ballista + Pyreheart Wolf

Agatha's Soul Cauldron

Walking Ballista

Pyreheart Wolf

How it works

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

This clever loop turns Pyreheart Wolf's own self-targeting activated ability—borrowed via Agatha's Soul Cauldron—into a lethal engine of destruction. With Agatha's Soul Cauldron having previously exiled Pyreheart Wolf to grant its activated ability, Walking Ballista can repeatedly strip away its own counters to ping the Wolf for damage. Because Agatha's Soul Cauldron also allows you to spend mana as though it were mana of any color and grants activated abilities to your creatures with +1/+1 counters, Walking Ballista becomes fully armed with the Wolf's power while utilizing its own native ability to distribute counters. Once the Wolf succumbs to lethal damage, its undying ability triggers to resurrect it with a fresh +1/+1 counter, resetting the loop for infinite death triggers, enter-the-battlefield effects, and leaves-the-battlefield triggers.