Totentanz, Swarm Piper + Nim Deathmantle + Ashnod's Altar

Totentanz, Swarm Piper

Nim Deathmantle

Ashnod's Altar

How it works

1. Activate Ashnod's Altar by sacrificing Totentanz, adding CC.
2. When Totentanz dies, it and Nim Deathmantle triggers.
3. Resolve the Totentanz trigger, creating a 1/1 Rat creature token.
4. Activate Ashnod's Altar by sacrificing the Rat, adding CC.
5. Resolve the Nim Deathmantle trigger from step 2, causing you to pay 4 to return Totentanz from your graveyard to the battlefield, and attach Nim Deathmantle to it.
6. Repeat.