Nim Deathmantle + Ashnod's Altar + Ferocious Pup

Nim Deathmantle

Ashnod's Altar

Ferocious Pup

How it works

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

This clever loop turns a modest canine into an endless engine of sacrifice and resurrection by exploiting the mana generated from Ashnod's Altar. You begin by feeding Ferocious Pup to the Altar for two colorless mana, which sends the Pup to the graveyard and triggers Nim Deathmantle's ability; by paying the required four mana, the Deathmantle pulls the Pup right back to the battlefield while reattaching itself. Every time the Pup returns, its entry ability conjures a 2/2 green Wolf creature token, which you can immediately feed back into Ashnod's Altar to help fund the next resurrection loop. Because the Altar's sacrifice yields two colorless mana and the Deathmantle costs four to activate, you need an extra source of two mana (or a reduced cost) to sustain the loop indefinitely, ultimately producing infinite death, entry, leave-the-battlefield, and sacrifice triggers.