Eternal Scourge + Young Deathclaws + Crystalline Crawler + Viscera Seer + Doubling Season

Eternal Scourge

Young Deathclaws

Crystalline Crawler

Viscera Seer

Doubling Season

How it works

1. Activate Eternal Scourge's scavenge ability, granted to it by Young Deathclaws, by paying 3 and exiling Eternal Scourge from your graveyard, putting six +1/+1 counters on Crystalline Crawler due to Doubling Season.
2. Activate Crystalline Crawler six times by removing six +1/+1 counters from it, adding 6.
3. Cast Eternal Scourge from exile by paying 3.
4. Activate Viscera Seer by sacrificing Eternal Scourge.
5. Repeat.

This intricate loop turns the graveyard into an endless engine by leveraging Young Deathclaws to grant Eternal Scourge a scavenge ability equal to its mana cost. Because Doubling Season doubles all counters placed on permanents, scavenging the Scourge onto Crystalline Crawler yields double the +1/+1 counters, which the Crawler can then convert into an excess of colored mana. You can cast Eternal Scourge right back out of exile since its own ability permits it, letting Viscera Seer sacrifice it repeatedly to fuel the loop while digging through your deck with infinite scry triggers.