Prosper, Tome-Bound + Portcullis + Eternal Scourge + Eye of Ugin

Prosper, Tome-Bound

Portcullis

Eternal Scourge

Eye of Ugin

How it works

1. Cast Eternal Scourge either from your hand or from exile by paying 1.
2. If you played Eternal Scourge from exile, Prosper's second ability triggers, creating a Treasure token.
3. Eternal Scourge enters the battlefield, triggering Portcullis, exiling Eternal Scourge.
4. If you created a Treasure token, activate it by tapping and sacrificing it, adding 1.
5. Repeat.