Stalwart Successor + Altar of Dementia + Grazing Kelpie

Stalwart Successor

Altar of Dementia

Grazing Kelpie

How it works

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

This clever loop turns the self-replacing nature of persist into a mill engine by utilizing Stalwart Successor as the crucial glue that cancels out the drawback of Grazing Kelpie's -1/+1 counter interactions. Whenever Grazing Kelpie returns from the grave, the first-time counter trigger from Stalwart Successor places a +1/+1 counter on it, which immediately neutralizes the -1/-1 counter from persist via state-based actions. This leaves the Kelpie fresh and free of counters so its persist can trigger all over again each time Altar of Dementia sacrifices it to mill your opponents out entirely.