Ajani, Adversary of Tyrants’ first ability is a good one, especially if the creatures you get to pump have vigilance, such as a Knight token or Heart of Kiran, so that you can apply pressure and protect your planeswalker. Ajani’s first ability also synergizes well with Walking Ballista.
Ajani’s second ability doesn’t synergize with History of Benalia, Heart of Kiran, or Walking Ballista, but it does go along with Knight of Glory and Knight of Malice, and all things considered you can put together a very nice B/W shell.
The ultimate isn’t really relevant, as Ajani will likely die to a Vraska’s Contempt or you’ll kill it to make sure you never run out of creatures, and the games where you pump your creatures that many times shouldn’t be hard to win either way.
B/W Midrange has been a deck since the beginning of Dominaria Standard. I played it at GP Birmingham, and it was terrible for me. On top of that, the deck didn’t put up any real numbers in the metagame. Maybe now, with Ajani, Adversary of Tyrants, things will change!
The Toolcraft Exemplar + Scrapheap Scrounger shell has to be removed because of how bad it is versus red decks. It isn’t just Goblin Chainwhirler killing Toolcraft Exemplar for free—it’s Scrapheap Scrounger, and on some level Heart of Kiran, which are now bad versus any red deck.
You would love to pair your midrange deck with a card like Scrapheap Scrounger since it’s good to curve out and useful in the late-game, but you can’t because of how fast some decks are, and you can never afford to play creatures that can’t trade.
With all this said, let’s build a B/W Midrange deck!
Another tool that M19 brings to Standard is Shield Mare, a powerful card versus red decks that can give you up to 6 life points, which is very important in a matchup that often revolves around surviving until the late-game where your higher mana curve will take over.
The unblockable clause isn’t irrelevant because Goblin Chainwhirler can often hold off your entire squad, and Shield Mare can be pumped enough by Ajani to become a real threat.
Many B/W decks aren’t playing Lyra Dawnbringer anymore, and that makes sense in a format with Unlicensed Disintegration and Ravenous Chupacabra, but I figured that with three copies of Ajani, Adversary of Tyrants, your creatures become threats fast and your opponent can no longer ignore those Knights. They have to answer them, and when they do, you’ll play Lyra later in the game, hoping to dodge a topdecked removal and take over the game.
This is a very simple list, but it’s a good starting point for what I think will be a good archetype in M19 Standard.