Prototype Portal + Dross Scorpion + Myr Moonvessel + Yahenni, Undying Partisan

Prototype Portal

Dross Scorpion

Myr Moonvessel

Yahenni, Undying Partisan

How it works

1. Activate Prototype Portal by paying 1 and tapping it, creating a token copy of Myr Moonvessel.
2. Activate Yahenni 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 Yahenni ability, giving it indestructible until end of turn.
7. Repeat.