Appa, Steadfast Guardian + Eternal Scourge + Ashnod's Altar + Rest in Peace

Appa, Steadfast Guardian

Eternal Scourge

Ashnod's Altar

Rest in Peace

How it works

1. Cast Eternal Scourge from exile by paying 3.
2. Appa's second ability triggers, creating a 1/1 Ally creature token.
3. Activate Ashnod's Altar twice by sacrificing Eternal Scourge and the Ally, adding CCCC.
4. Eternal Scourge is exiled instead of being put into your graveyard due to Rest in Peace.
5. Repeat.

This clever loop is fueled by Eternal Scourge, which can repeatedly crawl out of exile to pay its own casting cost of three mana. Ashnod's Altar converts those returning creatures into a steady surplus of colorless mana while setting up the sacrifice triggers. Meanwhile, Rest in Peace acts as the engine's quiet anchor, intercepting the Scourge as it dies and rerouting it straight back to exile so the cycle can restart. Finally, Appa, Steadfast Guardian provides the icing on the cake by turning every single one of those casts from exile into an army of 1/1 white Ally creature tokens.