Nim Deathmantle + Ashnod's Altar + Hallowed Spiritkeeper

Nim Deathmantle

Ashnod's Altar

Hallowed Spiritkeeper

How it works

1. Activate Ashnod's Altar by sacrificing Hallowed Spiritkeeper, adding CC.
2. When Hallowed Spiritkeeper dies, it and Nim Deathmantle trigger,
3. Resolve the Hallowed Spiritkeeper trigger, creating at least one creature token.
4. Holding priority, activate Ashnod's Altar by sacrificing a creature token, adding CC.
5. Resolve the Nim Deathmantle trigger, causing you to pay 4 to return Hallowed Spiritkeeper from your graveyard to the battlefield and attach Nim Deathmantle to it.
6. Repeat.