Altar of Dementia + Lesser Masticore + Thran Vigil

Altar of Dementia

Lesser Masticore

Thran Vigil

How it works

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