Mikaeus, the Unhallowed + Altar of Dementia + River Kelpie

Mikaeus, the Unhallowed

Altar of Dementia

River Kelpie

How it works

1. Activate Altar of Dementia by sacrificing River Kelpie.
2. When River Kelpie dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When River Kelpie enters, its first ability triggers, causing you to draw a card.
4. Resolve the Altar of Dementia ability.
5. Activate Altar of Dementia by sacrificing River Kelpie.
6. When River Kelpie dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
7. When River Kelpie enters, its first ability triggers, causing you to draw a card.
8. Resolve the Altar of Dementia ability.
9. Repeat.