Goblin Warrens + Phyrexian Altar + Kaya, Geist Hunter

Goblin Warrens

Phyrexian Altar

Kaya, Geist Hunter

How it works

1. Activate Kaya's second loyalty ability by removing two loyalty counters from it, causing you to double any tokens you create this turn.
2. Activate Goblin Warrens by paying 2 and sacrificing two Goblins, creating six 1/1 Goblin creature tokens.
3. Activate Phyrexian Altar three times by sacrificing three Goblins, adding 2.
4. Repeat from step 2.

This loop transforms a modest sacrifice outlet into a runaway engine by leveraging Kaya, Geist Hunter's minus ability, which doubles every token you bring into the world. You use Phyrexian Altar to churn sacrificed creatures into the exact red mana needed to feed Goblin Warrens, while that same Altar absorbs the extra bodies left over from the doubling effect to sustain the loop indefinitely. Because Goblin Warrens sacrifices two creatures to generate six doubled tokens, you constantly net a surplus of creatures to sacrifice for colored mana.