Underworld Breach + Diligent Excavator + Thassa's Oracle + Mercurial Pretender

Underworld Breach

Diligent Excavator

Thassa's Oracle

Mercurial Pretender

How it works

1. Cast the artifact creature from your hand by paying 0.
2. Diligent Excavator and Mercurial Pretender 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 loop transforms a free zero-mana artifact creature into an infinite engine by leveraging Underworld Breach, which lets you repeatedly escape that same creature from your graveyard by feeding it card fuel. To convert this churning cycle into a victory, Diligent Excavator mills your entire library as you endlessly cast and sacrifice historic spells. Meanwhile, Mercurial Pretender stands ready as a copy of the Excavator, doubling your milling output to speed through your deck. Once your library is completely gone, you drop Thassa's Oracle—either from your hand or escaped from your graveyard with Underworld Breach's help—and its enters-the-battlefield trigger instantly wins you the game.