Vhal, Candlekeep Researcher

Once the game begins, your two commanders are tracked separately. If you cast one, you won't have to pay an additional {2} the first time you cast the other. A player loses the game after having been dealt 21 combat damage from any one of them, not from both of them combined (although your Background won't usually be a creature anyway).

If you control a Background that grants an ability to commander creatures you own, and you own more than one commander creature, each of them will have that ability.

If your commander loses the choose a Background ability or stops being a Background during the game, as appropriate, it is still your commander.

You can choose two commanders that are the same color or colors.

If your Commander deck has two commanders, you can include only cards whose own color identities are also found in your commanders' combined color identities.

If a card refers to a commander creature you own, a Background won't usually be counted or included for that effect. If another spell or ability causes your Background to become a creature, however, it will be included. Any effect that refers to your commander or a commander you own or control without specifying creature will apply to a Background that is your commander, as appropriate.