Mikaeus, the Unhallowed + Safehold Elite + Phantom Train

Mikaeus, the Unhallowed

Safehold Elite

Phantom Train

How it works

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