Prototype Portal + Dross Scorpion + Goblin Bombardment + Myr Moonvessel

Prototype Portal

Dross Scorpion

Goblin Bombardment

Myr Moonvessel

How it works

1. Activate Prototype Portal by paying 1 and tapping it, creating a token copy of Myr Moonvessel.
2. Activate Goblin Bombardment 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 Goblin Bombardment ability, dealing 1 damage to any target.
7. Repeat.