Enduring Renewal + Crystalline Crawler + Phyrexian Altar

Enduring Renewal

Crystalline Crawler

Phyrexian Altar

How it works

1. Cast Crystalline Crawler by paying 4 in four different colors, causing Crystalline Crawler to enter the battlefield with four +1/+1 counters on it.
2. Activate Crystalline Crawler's first ability four times by removing four +1/+1 counters from it, adding 4 in four different colors.
3. Activate Phyrexian Altar by sacrificing Crystalline Crawler, adding one mana of any color.
4. When Crystalline Crawler dies, Enduring Renewal triggers, returning Crystalline Crawler from your graveyard to your hand.
5. Repeat.