Mikaeus, the Unhallowed + Crystalline Crawler + Carrion Feeder

Mikaeus, the Unhallowed

Crystalline Crawler

Carrion Feeder

How it works

1. If Crystalline Crawler has a +1/+1 counter on it, activate its first ability by removing a +1/+1 counter from it, adding one mana of any color.
2. Repeat step 1 until Crystalline Crawler has no +1/+1 counters on it.
3. Activate Carrion Feeder by sacrificing Crystalline Crawler.
4. Crystalline Crawler dies, triggering its undying ability, returning it to the battlefield with a +1/+1 counter on it.
5. Resolve the Carrion Feeder ability, putting a +1/+1 counter on it.
6. Repeat.