Nim Deathmantle + Ashnod's Altar + Agents of HYDRA

Nim Deathmantle

Ashnod's Altar

Agents of HYDRA

How it works

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