Stalwart Successor + Kithkin Spellduster + Carrion Feeder

Stalwart Successor

Kithkin Spellduster

Carrion Feeder

How it works

1. Activate Carrion Feeder by sacrificing Kithkin Spellduster
2. When Kithkin Spellduster dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Kithkin Spellduster enters, Stalwart Successor triggers, putting a +1/+1 counter on Kithkin Spellduster
4. Resolve the Carrion Feeder ability.
5. Repeat.

This elegant loop relies on Kithkin Spellduster returning via persist with a -1/-1 counter, which normally prevents further recurrences, but Stalwart Successor cleverly steps in to neutralize that drawback by placing a +1/+1 counter on it the moment it enters the battlefield. Because game rules annihilate opposing +1/+1 and -1/-1 counters on a creature as a state-based action, Kithkin Spellduster is left completely clean and ready to be sacrificed all over again. You can feed this endless cycle directly into Carrion Feeder to pump it to astronomical sizes while generating infinite sacrifices, enters-the-battlefield triggers, and leave-the-battlefield triggers.