Choose a Background

Choose a Background is a keyword ability introduced in Commander Legends: Battle for Baldur's Gate, as a Partner variant linked together with the Background legendary enchantment subtype. You can have a Background as a second Commander.
==Description==
"Choose a Background" only appears on monocolored legendary creatures (and on , which is colorless but becomes monocolored before the game begins). By choosing a Background, they can be customized to be your Commander.
A Background adds extra abilities to your Commander, and changes their color identity. It functions similar to Partner, modifying the rules for deck construction in the Commander variant, and functioning before the game begins. Rather than a single legendary creature card, you may designate a legendary creature card in combination with a Background as your Commander(s).
==Rules==
==Rulings==
* Some cards, usually Backgrounds themselves, refer to "Commander creatures." Those don't refer to a Background enchantment that is a Commander unless it is also a creature. 
* If a card refers to your Commander, it means either the legendary creature or the legendary Background enchantment. So cards like <c>Command Beacon</c> can fetch either the legendary creature or the legendary Background. Anything that cares about whether you control your Commander will be satisfied if you control one or both of them. Cards like <c>Command Tower</c> can add mana of either of your commanders' color identities.
* both has Choose a Background and is a Background. It can effectively be partnered with any Choose a Background commander, or be used with any Background, but cannot be used to have three (or more) commanders.
==References==