Chthonian Nightmare + Shambling Ghast + Greedy Freebooter + Skittering Precursor

Chthonian Nightmare

Shambling Ghast

Greedy Freebooter

Skittering Precursor

How it works

1. Cast Chthonian Nightmare by paying 1.
2. When Chthonian Nightmare enters the battlefield, it triggers, causing you to get EEE.
3. Activate Chthonian Nightmare by paying an amount of E, sacrificing Greedy Freebooter or Shambling Ghast and returning Chthonian Nightmare from the battlefield to your hand.
4. When Greedy Freebooter or Shambling Ghast dies, it and Skittering Precursor trigger.
5. Resolve the Greedy Freebooter or Shambling Ghast trigger, creating a Treasure token.
6. Resolve the Skittering Precursor trigger, creating a 0/1 Eldrazi Spawn creature token.
7. Resolve the Chthonian Nightmare ability, returning either Greedy Freebooter or Shambling Ghast from your graveyard to the battlefield.
8. Activate the Eldrazi Spawn by sacrificing it, adding C.
9. Activate the Treasure by tapping and sacrificing it, adding .
10. Repeat.