If your commander loses the choose a Background ability or stops being a Background during the game, as appropriate, it is still your commander.
Wilson, Refined Grizzly
Both commanders start in the command zone, and the remaining 98 cards (or 58 cards in a Commander Draft game) of your deck are shuffled to become your library.
Choose a Background is a variant of the partner ability. You may have two commanders if one of them is a legendary creature with the choose a background ability and the other is a legendary Background enchantment. Backgrounds and cards with choose a Background do not interact with cards which have any other partner ability.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Justine Mara Andersen
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
