Geralf, the Fleshwright + Putrid Goblin + Ashnod's Altar

Geralf, the Fleshwright

Putrid Goblin

Ashnod's Altar

How it works

1. Activate Ashnod's Altar by sacrificing Putrid Goblin, adding CC.
2. When Putrid Goblin dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Putrid Goblin enters the battlefield, Geralf's second ability triggers, putting a number of +1/+1 counters on it equal to the number of other Zombies that entered the battlefield under your cotnrol this turn.
4. Repeat.

This clever loop turns Putrid Goblin into an infinite sacrifice engine by exploiting the interaction between persist and Ashnod's Altar, generating endless colorless mana and death triggers along the way. Whenever the Goblin dies and returns with a -1/-1 counter, Geralf, the Fleshwright steps in with a crucial passive boost: its second ability triggers upon the Zombie's entry, placing +1/+1 counters that immediately cancel out the -1/-1 counters. Because these opposing counters annihilate each other state-based-wise, the Goblin is left completely clean of counters and ready to be sacrificed to the Altar all over again.