Color Identity: B

Initial Card State
- Walking Ballista in exile (exiled by Agatha's Soul Cauldron).
- Sengir and Agatha's Soul Cauldron on the battlefield.
Notable Prerequisites
- Sengir has at least one +1/+1 counter on it.
- You have a way to give Sengir deathtouch.
Steps
- Give Sengir deathtouch, if needed.
- Activate Sengir using Walking Ballista's second ability by removing a +1/+1 counter from it, dealing 1 damage to any creature an opponent controls, and killing it due to Sengir's deathtouch.
- When the creature dies, Sengir's first ability triggers, putting two +1/+1 counters on it.
- Repeat from step 2 as desired.
Notes
- If you have a way to give Sengir deathtouch indefinitely, you can repeat this loop whenever a creature enters the battlefield under an opponent's control.
Results
- Destroy each creature that enters the battlefield under an opponent's control.
- Destroy all creatures opponents control.
Bracket Tag
This combo has been estimated to be Spicy (Bracket 3-4+).