Nim Deathmantle + Ashnod's Altar + Iron League Steed

Nim Deathmantle

Ashnod's Altar

Iron League Steed

How it works

1. Activate Ashnod's Altar by sacrificing Iron League Steed, adding CC.
2. When Iron League Steed dies, Nim Deathmantle triggers, causing you to pay 4 to return Iron League Steed from your graveyard to the battlefield, and attach Nim Deathmantle to it.
3. When Iron League Steed enters the battlefield, its fabricate ability triggers, creating a 1/1 Servo artifact creature token.
4. Activate Ashnod's Altar by sacrificing the Servo, adding CC.
5. Repeat.

This ingenious loop turns Iron League Steed into a self-sustaining engine by taking advantage of the creature's own entry trigger. When you sacrifice Iron League Steed to Ashnod's Altar, you generate two colorless mana toward the four required by Nim Deathmantle's revival trigger. The missing mana is easily paid for by sacrificing the 1/1 Servo artifact creature token created when Iron League Steed's fabricate 1 ability resolves upon returning to the battlefield. By cycling the Steed and its generated token through the Altar, the mantle keeps wrapping around the returning creature to repeat the process indefinitely.