Prototype Portal + Dross Scorpion + Myr Moonvessel + Carrion Feeder

Prototype Portal

Dross Scorpion

Myr Moonvessel

Carrion Feeder

How it works

1. Activate Prototype Portal by paying 1 and tapping it, creating a token copy of Myr Moonvessel.
2. Activate Carrion Feeder by sacrificing Myr Moonvessel.
3. When Myr Moonvessel dies, Myr Moonvessel and Dross Scorpion trigger.
4. Resolve the Myr Moonvessel trigger, adding C.
5. Resolve the Dross Scorpion trigger, untapping Prototype Portal.
6. Resolve the Carrion Feeder ability, putting a +1/+1 counter on it.
7. Repeat.