Cauldron of Souls + Dross Scorpion + Workhorse

Cauldron of Souls

Dross Scorpion

Workhorse

How it works

1. Activate Cauldron of Souls by tapping it, Workhorse gain persist until end of turn.
2. Activate Workhorse by removing a +1/+1 counter, adding C.
3. Repeat from step 2 until Workhorse dies.
4. Dross Scorpion and Workhorse triggers.
5. Resolve the Dross Scorpion trigger, untapping Cauldron of Souls.
6. Resolve the Workhorse persist ability trigger, returning it to the battlefield with three +1/+1 counters on it.
7. Repeat.