Mikaeus, the Unhallowed + River Kelpie + Phantom Train

Mikaeus, the Unhallowed

River Kelpie

Phantom Train

How it works

1. Activate Phantom Train 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 Phantom Train ability.
5. Activate Phantom Train 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 Phantom Train ability.
9. Repeat.