Mikaeus, the Unhallowed + Altar of Dementia + Persistent Constrictor

Mikaeus, the Unhallowed

Altar of Dementia

Persistent Constrictor

How it works

1. Activate Altar of Dementia by sacrificing Persistent Constrictor.
2. When Persistent Constrictor dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Resolve the Altar of Dementia ability.
4. Activate Altar of Dementia by sacrificing Persistent Constrictor.
5. When Persistent Constrictor dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Resolve the Altar of Dementia ability.
7. Repeat.