No, background is a different mechanic that was introduced in Commander Legends: Battle for Baldur's Gate that allows for an enchantment card to influence your deck's color identity
Exsanguinator Cavalry is impressive, its effects have great synergies with the deck, plus redundancy for Eminence's effects, filtering the hand, crowding the graveyard, and making its tribe mates huge
Chandra, Hopes Beacon I could have easily included Chandra, Dressed to Kill in these rankings for its speed and burn-ramp for aggressive decks
This is one of the most straight-forward Doctor and companion pairings in the decks: Yaz exiles cards, The Thirteenth Doctor puts counters on stuff for playing that exiled card, and then untaps all your creatures with counters on to help them swing in
Galloping Lizrog Galloping Lizrog basically doubles the number of +1/+1 counters on your side of the field, but in a very eggs-in-one-basket approach
Target creature gets -4/-4 until end of turn