Dross Scorpion + Triskelion + Cauldron of Souls

Dross Scorpion

Triskelion

Cauldron of Souls

How it works

1. Activate Cauldron of Souls by tapping it, giving Triskelion and any number of other target creatures persist until end of turn.
2. Activate Triskelion until there is only one +1/+1 counter remaining on it, dealing 1 damage to any target for each activation.
3. Activate Triskelion again by removing the last +1/+1 counter from it.
4. Triskelion dies due to having 0 toughness, triggering its own persist ability and Dross Scorpion.
5. Resolve Dross Scorpion's ability, untapping Cauldron of Souls.
6. Resolve Triskelion's persist ability, returning it from your graveyard to the battlefield with three +1/+1 counters and one -1/-1 counter on it.
7. The -1/-1 counter and one +1/+1 counter are removed from Triskelion as a state-based action.
8. Resolve the Triskelion ability from step 3, dealing 1 damage to any target.
9. Repeat.