Underworld Breach + Culling the Weak + Stitcher's Supplier

Prerequisites

You have at least three additional cards in your graveyard.

Steps

1. Cast Culling the Weak for its escape cost by paying {B}, exling three other cards from your graveyard, and sacrificing Stiticher's Supplier.
2. Stitcher's Supplier dies, causing you to mill three cards.
3. Resolve Culling the Weak, adding {B}{B}{B}{B}.
4. Cast Stitcher's Supplier for its escape cost by paying {B} and exling three other cards from your graveyard.
5. Stitcher's Supplier enters the battlefield, causing you to mill three cards.
6. Repeat.