Card Spotlight
A 2-mana red enchantment that gives every nonland card in your graveyard escape for its mana cost plus exiling three other graveyard cards, then sacrifices itself at the end step. With Lion's Eye Diamond and Brain Freeze, it loops for unlimited mana and mill.
Commander Spotlight
Underworld Breach ↗
A 2-mana red enchantment that gives every nonland card in your graveyard escape for its mana cost plus exiling three other graveyard cards, then sacrifices itself at the end step. With Lion's Eye Diamond and Brain Freeze, it loops for unlimited mana and mill.
See Underworld Breach's full stats and printings →
Underworld Breach is an enchantment, so it can never be a commander. It is played in the 99 of red combo decks, usually with blue.
It belongs in Izzet or Grixis combo decks that already run Lion's Eye Diamond, Brain Freeze or Thassa's Oracle, where it is a two-mana engine that ends the game the turn it resolves. In a fair deck it is a one-turn burst of graveyard spells that you sacrifice at the end step.
Lion's Eye Diamond ↗
Discard your hand and sacrifice it for three mana of one color, then escape it for {0}. It is a Game Changer.
Brain Freeze ↗
Escapes for {1}{U} plus three other cards. Its storm copies mill three cards each, which keeps the graveyard full for the next pass.
Thassa's Oracle ↗
The cleanest finish: mill your own library, then escape the Oracle for {U}{U} and win on its trigger.
Dark Ritual ↗
Escapes for {B} and adds {B}{B}{B}, so it nets black mana each time you can exile three cards for it.
Underworld Breach is mid-priced. Its original Theros Beyond Death printing has been joined by Special Guests, Mystery Booster 2 and Secret Lair versions. Lion's Eye Diamond is the expensive part of the combo: it is on the Reserved List, which keeps it from being reprinted.
With Breach on the battlefield: activate Lion's Eye Diamond for {U}{U}{U}, discarding your hand and sacrificing it. Cast Brain Freeze from your graveyard with escape for {1}{U} plus three other graveyard cards, targeting yourself. Then cast Lion's Eye Diamond back with escape for {0} plus three more cards. Each pass nets one blue mana and two more spells cast this turn, and Brain Freeze's storm copies mill more cards than the loop exiles once the storm count climbs.
Point Brain Freeze copies at your opponents to mill their libraries, and each loses the next time they would draw from an empty library. For an immediate win, mill your own library instead and escape Thassa's Oracle for {U}{U} plus three cards: with no cards in your library, its trigger wins the game.
Yes. Underworld Breach, Lion's Eye Diamond and Thassa's Oracle are all on the Game Changers list, so Brackets 1 and 2 can't run them and Bracket 3 decks can run three Game Changers in total. The full combo uses two or three of those slots on its own, which is why it is almost always a Bracket 4 or cEDH line.