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).
Cloakwood Hermit
The ability Cloakwood Hermit grants triggers if you control a creature with that ability as the end step begins and a creature card was put into your graveyard from anywhere this turn. This is true even if no creatures had this ability at the time the creature card went to the graveyard or the creature card is no longer in your graveyard as your end step begins.
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.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Kai Carpenter
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
