You can read the first Article from the Oathbreaker Rules Committee here: The Art of Banning.
Oathbreaker was founded as a fun and fast casual multiplayer format. As with any format, cards can be broken with enough time and effort in a competitive setting. If you enjoy playing competitively and want to try Oathbreaker in that light, just be sure to ask your playgroup first, as Oathbreaker is intended to be a social and multiplayer casual format.
The Oathbreaker format wants to be multiplayer, casual, friendly, interactive, memorable, Planeswalker-focused, and quick. Our banned list list aims to reflect these aspirations.
The Oathbreaker Rules Committee considers the following categories when banning cards:
- Extreme early mana acceleration. This is typically permanent mana sources that produce more mana than they cost to cast. Limiting fast mana early in games is necessary given players have access to multiple spells in the command zone and decks are only 58 cards. Fast mana has the tendency to end games too quickly. Ban examples: Sol Ring , Mana Crypt  and original Moxen.
- Instant and Sorcery Cards that win the game with minimal work. These are cards that need to be immediately answered or else the game ends. These types of cards usually lead to stale or monotonous game play. Ban examples: Ad Nauseam  and Biorhythm .
- Planeswalkers that interact too well as an Oathbreaker. These are planeswalker cards that easily abuse the rules of the format, especially the Signature spell card. Because Oathbreaker tries to focus on the power of planeswalkers, we want to avoid banning planeswalkers whenever possible. However, sometimes this becomes necessary. Ban examples: Saheeli the Gifted .
- Cards that essentially restart the game. **THIS SECTION UNDER REVIEW**. These cards typically invalidate all previous gameplay, reset the game state drastically so most players have limited options, and extend games too long. Ban examples: Worldfire  and Upheaval 
- Cards that lead to unreactive game states or unmemorable games. Cards that take over games in an undesirable way, that leave most players locked out of the game and unenthused. These types of cards are usually too hard to answer, under costed, or enable quick combo finishes. Ban examples: Trade Secrets  and Limited Resources .
Banning New Cards
The Oathbreaker Rules Committee believes all cards deserve a chance to be enjoyed. Cards will not be banned for at least 3 months from its pre-release date. Only under the most dire circumstances will an emergency ban be issued for a new card.