Chthonian Nightmare + Priest of Gix + Skittering Precursor + Umbral Collar Zealot

Chthonian Nightmare

Priest of Gix

Skittering Precursor

Umbral Collar Zealot

How it works

1. Activate Umbral Collar Zealot by sacrificing Priest of Gix.
2. When Priest of Gix dies, Skittering Precursor triggers, creating a 0/1 Eldrazi Spawn creature token.
3. Resolve the Umbral Collar Zealot ability
4. Activate Chthonian Nightmare by paying EEE, sacrificing the Eldrazi Spawn and returning Chthonian Nightmare from the battlefield to your hand, returning Priest of Gix from your graveyard to the battlefield.
5. When Priest of Gix enters the battlefield, it triggers, adding .
6. Cast Chthonian Nightmare by paying 1.
7. When Chthonian Nightmare enters the battlefield, it triggers, causing you to get EEE.
8. Repeat.

This cunning loop harnesses Chthonian Nightmare to repeatedly recycle Priest of Gix, using the dark priest's initial burst of black mana to fund the enchantment's re-casting cost. While Umbral Collar Zealot provides a convenient outlet to sacrifice your creatures, it is Skittering Precursor that truly glues the loop together by transforming those sacrifices into Eldrazi Spawn tokens, providing the exact bodies and energy-free sacrifice fodder needed to continuously trigger the Nightmare.