Nim Deathmantle + Ashnod's Altar + Doomed Traveler

Nim Deathmantle

Ashnod's Altar

Doomed Traveler

How it works

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