Mystery Booster Commander Game Changes
Wizards published the rules bulletin on October 19 — new ability word, updated comprehensive rules, and legality dates for the set.
New ability word: Rulebreaker
The headline change — abilities that alter deck construction rules, only active when the card is your commander. New rule 903.5e makes them function before the game begins.
| Example | What it does |
|---|---|
| Seluma, Light of Aysen | Deck can include Angel cards of any color identity and any basic lands |
| Whtz, the Bibliophile | Deck has no maximum deck size |
| Tolabow, Loch Rascal | Instant/sorcery color identity may include one chosen extra color + any basic lands (Oracle text was updated for clarity) |
Comprehensive rules updates
| Rule | Change |
|---|---|
| 903.5e (new) | Rulebreaker abilities work at the appropriate time — before the game begins — when the card is your commander |
| 122.1g | Fixed to match 704.5w — a non-Siege battle with 0 defense counters goes to its owner's graveyard |
| 201.4f | "Choose a card name" can now name the Adventure on an adventurer card (consistency with Omen/prepared spells) |
| 205.3j | Seven new planeswalker subtypes: Arzakon, Dyfed, Feroz, Greensleeves, Sifa, Thomil, Worzel |
| 207.2c | Rulebreaker added to the list of ability words |
Legality dates
| Format | MBC cards legal from |
|---|---|
| Commander | November 13, 2026 |
| Legacy / Vintage / Eternal | January 1, 2027 |
| Playtest & acorn cards | Not legal anywhere |
Also returning: Partner
Partner is back — decks can run two commanders when both have partner. Combined with Rulebreaker, expect some unconventional commanders this set.