Mikaeus, the Unhallowed + Shilgengar, Sire of Famine + River Kelpie

Mikaeus, the Unhallowed

Shilgengar, Sire of Famine

River Kelpie

How it works

1. Activate Shilgengar 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 Shilgengar ability.
5. Activate Shilgengar 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 Shilgengar ability.
9. Repeat.

This looping engine relies on Mikaeus, the Unhallowed granting undying to River Kelpie, which neatly counterbalances the Kelpie's native persist ability to keep it churning endlessly between the battlefield and the graveyard. As River Kelpie repeatedly enters the battlefield from the graveyard, its triggered ability draws you a card while Shilgengar, Sire of Famine happily sacrifices the creature to churn out a steady stream of Blood tokens. Because Mikaeus bestows alternating +1/+1 and -1/-1 counters on the Kelpie with each recursion, you can endlessly repeat the sacrifice and return loop without the creature ever permanently staying dead.