Underworld Breach + Diligent Excavator + Thassa's Oracle + Undercover Operative

Underworld Breach

Diligent Excavator

Thassa's Oracle

Undercover Operative

How it works

1. Cast the artifact creature from your hand by paying 0.
2. Diligent Excavator and Undercover Operative 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 potent loop leverages Underworld Breach to repeatedly recast a zero-mana artifact creature from your graveyard, continually feeding its escape cost by churning through the cards you toss away. As you cast it over and over, Diligent Excavator and its clone, Undercover Operative, trigger on every single historic spell to mill your entire library into the graveyard. Once your library is completely empty, you finish off the opponent by casting Thassa's Oracle, whose enters-the-battlefield trigger instantly wins you the game because your devotion to blue exceeds your remaining library size.