Chthonian Nightmare + Greedy Freebooter + Shambling Ghast + Birgi, God of Storytelling // Harnfel, Horn of Bounty

Chthonian Nightmare

Greedy Freebooter

Shambling Ghast

Birgi, God of Storytelling // Harnfel, Horn of Bounty

How it works

1. Cast Chthonian Nightmare by paying 1.
2. Birgi triggers, adding .
3. When Chthonian Nightmare enters the battlefield, it triggers, causing you to get EEE.
4. Activate Chthonian Nightmare by paying E, sacrificing Greedy Freebooter and returning Chthonian Nightmare from the battlefield to your hand.
5. When Greedy Freebooter dies, it triggers, causing you to scry 1 and create a Treasure token.
6. Resolve the Chthonian Nightmare ability, returning Shambling Ghast from your graveyard to the battlefield.
7. Activate the Treasure by tapping and sacrificing it, adding .
8. Cast Chthonian Nightmare by paying 1.
9. Birgi triggers, adding .
10. When Chthonian Nightmare enters the battlefield, it triggers, causing you to get EEE.
11. Activate Chthonian Nightmare by paying E, sacrificing Shambling Ghast and returning Chthonian Nightmare from the battlefield to your hand.
12. When Shambling Ghast dies, it triggers, creating a Treasure token.
13. Resolve the Chthonian Nightmare ability, returning Greedy Freebooter from your graveyard to the battlefield.
14. Activate the Treasure by tapping and sacrificing it, adding .
15. Repeat.

This loop functions as a perpetual motion machine in the graveyard by constantly recycling low-cost threats while generating a surplus of resources. Chthonian Nightmare acts as the recursive engine, using its initial energy counters to sacrifice your creatures and return itself to hand, while Birgi, God of Storytelling provides the vital red mana rebate every time you recast the enchantment. Meanwhile, Greedy Freebooter and Shambling Ghast serve as interchangeable sacrifices that feed the Nightmare and replace themselves by generating Treasure tokens upon death, which easily cover the black mana needed to complete the loop.