Magic: The Gathering adopts the Oathbreaker format

Oathbreaker is intended as a casual multiplayer style of game for Magic: The Gathering. Up to 3 to 5 players can participate in an Oathbreaker game. Each player must have a 60-card deck, one of which is the Planeswalker their deck will focus on. Plus, one instant or sorcery card of the player's choice will be their Planeswalker's signature spell.

All MTG sets and cards are allowed in the Oathbreaker format, including Secret Lair and Universes Beyond cards such as the Warhammer 40K and The Lord of the Rings: Tales of Middle-earth crossover sets.

Once the player has chosen their Planeswalker (the titular "oathbreaker" of their deck) and the signature instant or sorcery spell, that leaves 58 cards for the rest of the deck. The signature spell and the rest of the cards must match the color identity of the chosen Planeswalker.

For example, if the player chose Teferi, Time Raveler from the War of the Spark set as their oathbreaker, all the other cards in the deck must have only blue or white mana symbols in the mana cost (and any mana symbols on the card's rules text). Colorless cards and basic lands are exceptions to this rule. On that note, no two cards in the deck may have the same name (also referred to as the singleton rule) except for basic lands.

The Oathbreaker Planeswalker card and the signature spell are both placed face up on the command zone. Similar to the Commander format, the player may cast the Oathbreaker Planeswalker from the command zone for its printed costs. However, each subsequent casting from the command zone costs 2 additional colorless mana. Thus, if the Oathbreaker will be cast a third time, it will require 4 colorless mana plus the card's printed mana cost.

Also similar to the Commander rules, when an Oathbreaker would leave play from the battlefield due to losing all its loyalty counters, being sent to the graveyard, the library, exiled, or similar effects, the player may return it to the command zone instead.

The signature spell can be cast whenever the Oathbreaker is in play. When the signature spell resolves, it is placed back on the command zone. This overrides any effects that would otherwise send it elsewhere, such as being counterspelled, returning to the owner's hand or library, or being exiled from the game. And just like the Oathbreaker itself, the signature spell increases its cost by 2 colorless mana for beyond the first time it was cast.

All the Oathbreaker players begin with 20 life, with the order of turns following a clockwise progression. As it is a free-for-all format, players in an Oathbreaker game can target and attack any other player, regardless of how they are positioned on the table. They may even attack multiple players during the combat phase. The game ends when only one player remains.

Although the Oathbreaker format has similar roots as the popular Commander format (otherwise known as Elder Dragon Highlander/EDH), WoTC has not yet announced any plans to release sets and exclusive cards specifically for it or if it will be adopted for Magic: The Gathering Arena.

Magic: The Gathering will be releasing March of the Machine, the latest expansion that closes out the Phyrexian invasion saga, on April 21, 2023.