Underworld Breach + Diligent Excavator + Thassa's Oracle + Altered Ego

Underworld Breach

Diligent Excavator

Thassa's Oracle

Altered Ego

How it works

1. Cast the artifact creature from your hand by paying 0.
2. Diligent Excavator and Altered Ego 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 elegant loop turns the graveyard into your personal library through Underworld Breach, granting escape to a free-to-cast artifact creature that repeatedly dips into your graveyard and feeds itself right back out. As you churn this creature in and out of the graveyard, Diligent Excavator turns every single cast—and every copy entering via Altered Ego if needed—into a relentless self-milling engine that strips your deck bare. Once your library is completely empty and your graveyard is fully stocked, you seal the victory by deploying Thassa's Oracle, whose enters-the-battlefield trigger instantly wins the game since your devotion to blue easily eclipses your zero remaining cards.