Ruthless Knave + Gravecrawler + Pawn of Ulamog + Sifter of Skulls

Ruthless Knave

Gravecrawler

Pawn of Ulamog

Sifter of Skulls

How it works

1. Activate Ruthless Knave's first ability by paying 2 and sacrificing Gravecrawler.
2. Gravecrawler dies, triggering Pawn of Ulamog and Sifter of Skulls.
3. Resolve the Pawn of Ulamog trigger, creating a 0/1 Eldrazi Spawn creature token.
4. Resolve the Sifter of Skulls trigger, creating a 1/1 Eldrazi Scion creature token.
5. Resolve the Ruthless Knave ability from step 1, creating two Treasure tokens.
6. Activate the Eldrazi Scion and Eldrazi Spawn by sacrificing them, adding CC.
7. Activate the Treasure tokens by tapping and sacrificing them, adding .
8. Cast Gravecrawler from your graveyard by paying .
9. Repeat.

This loop relies on an engine of cascading triggers and sacrifice outlets to endlessly recycle Gravecrawler from your graveyard. Whenever you pay to sacrifice Gravecrawler to Ruthless Knave, Pawn of Ulamog and Sifter of Skulls both trigger to populate your board with Eldrazi Spawn and Eldrazi Scion tokens. Meanwhile, the Knave turns that sacrifice into a pair of Treasure tokens, which together with the mana from the sacrificed tokens easily fund the black mana required to cast Gravecrawler right back out of the graveyard.