Underworld Breach + Diligent Excavator + Thassa's Oracle + Mirror Image

Underworld Breach

Diligent Excavator

Thassa's Oracle

Mirror Image

How it works

1. Cast the artifact creature from your hand by paying 0.
2. Diligent Excavator and Mirror Image 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 ingenious loop utilizes Underworld Breach to turn a free, zero-mana artifact creature—such as one cast and recast over and over—into an endless engine fueled by your own graveyard. As you repeatedly cycle that creature from your graveyard using escape, Diligent Excavator mills your entire library into the graveyard two cards at a time. Mirror Image can even step in as an additional copy if needed to accelerate the process or protect your setup. Once your library is completely empty, you simply cast Thassa's Oracle—either normally or escaping it via Underworld Breach—and let its enters-the-battlefield trigger instantly secure the win.