Nim Deathmantle + Ashnod's Altar + Penumbra Spider

Nim Deathmantle

Ashnod's Altar

Penumbra Spider

How it works

1. Activate Ashnod's Altar by sacrificing Penumbra Spider, adding CC.
2. When Penumbra Spider dies, it and Nim Deathmantle trigger,
3. Resolve the Penumbra Spider trigger, creating a 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 Penumbra Spider from your graveyard to the battlefield and attach Nim Deathmantle to it.
6. Repeat.