Mikaeus, the Unhallowed + Altar of Dementia + Glen Elendra Archmage

Mikaeus, the Unhallowed

Altar of Dementia

Glen Elendra Archmage

How it works

1. Activate Altar of Dementia by sacrificing Glen Elendra Archmage.
2. When Glen Elendra Archmage 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 Glen Elendra Archmage.
5. When Glen Elendra Archmage 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.