Underworld Breach + Diligent Excavator + Thassa's Oracle + Spark Double

Underworld Breach

Diligent Excavator

Thassa's Oracle

Spark Double

How it works

1. Cast the artifact creature from your hand by paying 0.
2. Diligent Excavator and Spark Double trigger, causing you to mill four cards.
3. The artifact creature enters the battlefield and dies as a state-based action due to having zero toughness.
4. Cast the artifact creature from your graveyard for its escape cost by paying 0 and exiling any three cards from your graveyard, except Thassa's Oracle if it is in your graveyard.
5. Repeat from step 2 until you have an empty library.
6. If Thassa's Oracle is in your hand, cast it by paying .
7. Otherwise, cast Thassa's Oracle from your graveyard for its escape cost by paying and exiling three cards from your graveyard.
8. Thassa's Oracle enters the battlefield, causing you to win the game.

This intricate loop transforms a humble zero-mana artifact creature into a self-contained win condition by leveraging Underworld Breach to continually recast it from your graveyard, fueling its own escape costs by churning through cards. Every iteration triggers Diligent Excavator to mill you further, while Spark Double duplicates that mill effect twofold to accelerate the process and empty your library in a flash. Once your deck is entirely in the graveyard, you simply deploy Thassa's Oracle—either naturally or escaped via Underworld Breach—and its enters-the-battlefield ability checks your blue devotion against your empty library to instantly claim victory.