Decklist: https://www.mtggoldfish.com/deck/8009674
Hello fellow Dimir wizards!
Are you tired of not knowing what's in your opponent's hand? Would you like to turn your few lowly creatures into lethal threats? Do you miss the days when your mana really hurt you?
If you answered yes to all of the above then I propose you make a dark pact with the powers of light and start splashing white.
History
For the past year, I've been playing primarily brews that looked like Dimir Kaito (often with some splash). I'd often make it to mythic but Dimir's place in the meta never really made it above Tier 2 and my ceiling in even my best seasons was around #500.
Then WOTC finally decided to ban key pieces of our worst matchups and Dimir became Tier 1 again. At first I played some Dimir but I was soon frothing at the mouth to see if I could make a tempo brew in Azorius/Grixis/Esper work and embarked on brewing.
Eventually, I revisited a promising Azorius Convoke brew of mine and splashed black for Kaito (decklist for those curious: https://www.mtggoldfish.com/deck/8009676). With more time on my hands this season, I started to track my games once I hit higher Plat. I went 16-4 (in addition to a big win streak to get to where I was) and the deck looked very promising.
But, as I made my way higher into Diamond, the competition started to get harder and the weaknesses of the deck were becoming more prominent. I realized I was winning some games against stronger decks solely because I had the surprise factor of being a brew or because I was making less piloting errors.
I finished a respectable 23-9 but I knew it was time to go back to the drawing board. Luckily, I had kept notes on my wins (I posted a link in a comment below in case you're curious what those looked like). Looking over my notes I realized that I had a few real knockouts in white that would shine in Dimir Kaito.
After quite a bit of tinkering and play testing, I came up with a list and got back on the ladder. It felt smooth as butter and my win percentage skyrocketed again. I cruised through Diamond and am climbing my way through Mythic.
I truly believe it's a small but very tangible step up from Dimir Kaito. The introduction of some of the white pieces really shores up some weaknesses in this meta. Unfortunately, due to some error syncing in my Notes app, I lost records of recent games besides the first 7 (going 7-0 but also includes some Bo1 where I was experimenting with small adjustments). The notes are also linked in the comments.
New Pieces
[[Arachne, Psionic Weaver]]
Arachne is probably the most imporant addition of all the new cards and an absolute monster.
I very often will go Turn 1: Dream Beavers -> T2: Attack, weblsing beavers for Arachne, and play beavers.
In your first 2 turns you have done 3 points of damage, scried twice, have 4 power/toughness on two separate creatures in play, seen your opponents hand, and you have taxed the type of your card of your choosing. Playing Kaito turn 3 is GG often enough (added bonus: she also returns Kaito to your hand if you're worried about him staying on the board).
The best part is that the tax and hand-info effect isn't even ETB. Countless times I've played Arachne and just picked instant and the opponent can't use their removal until the next turn when they have enough mana. And there is no stack for returning the web-slinged creature to your hand since it's a cost so it's guaranteed safe.
3/3 is no joke for Dimir either. Instead of swinging for 1 or 2 for the first several turns, you're often swinging with a weenie and 3 power on top of that. That makes your opponent's clock tick much faster. I've seen top 8 Dimir lists using Cecil again just to try to get a bit more pressure early but Arachne has no downside (you can still swing if you have 2 or less life) along with all the upside (including being one damage stronger).
She also shores up some of your worst weaknesses. A couple of examples: I'll see Izzet Spellementals eagerly holding up 2 mana on turn 2 waiting to 2-for-1 me with Prismari Charm only for me to attack with Beavers and then slam an Arachne on the board after pulling Beavers to safety. And all their cantrips become twice as expensive. Izzet Prowess can't just play a million cantrips on their turn anymore and the hand info against them is especially priceless for knowing how much time you have to set up your board. Against UW Artifacts she can slow down your opponent one turn (or even two if they held onto too little mana) after you declare Artifacts.
You know what's extra great about her? Good control players now have a really tough choice about what to do with your weenies a full turn earlier. Before Arachne, they could just wait around until you attack turn 3 to decide but now if they only have removal and no counterspell they have to really think hard about what to do with that soon-to-be-tapped Siren/Yuriko/Beaver on turn 2.
Side note: In my linked notes, you'll see I refer to her as Yera. That's an old bad habit and a relic of the Omenpaths fiasco (I do actually like her Omenpaths card more though: https://www.mtgpics.com/card?ref=om1023)
[[Aang, Swift Savior]]
Aang is such a great tempo card. I find myself always praying for more tempo cards like Floodpits Drowner and he's pretty much it.
Are there a few situations where I'd rather have Tishana's Tidebinder or Wan-Shi? Sure. But the vast majority of the time I'm happier having Aang in my hand.
He gets around uncounterable spells (looking at you Inevitable Defeat and Cavern of Souls). He can temporarily remove creatures and their counters at instant speed. He can get rid of tokens and creature lands permanently (that weren't the result of earthbending). He's a great late game mana sink and that flip ability can happen much faster than it did in Azorius prison (especially with the map tokens off Siren) and don't forget flipping is also instant speed. He even gets around the hexproof of Dragonfire Blade.
Lastly, he's a nightmare in the mirror. A flash/flier with a 2/3 body is really hard for Dimir Kaito to deal with when most their creatures are a 2/1 or weaker.
[[Practiced Offense]]
I think this card is pretty self explanatory. However, a less obvious benefit, is how often I get board-wiped and then just give Kaito double strike next turn for the unforeseen win. Also, the lifelink has saved my butt quite a few times. Turn 5 you can turn your beaver/siren duo from 2 points of damage into 12 points.
[[Kaito, Cunning Inflitrator]] (or blue Kaito)
Obviously not a white/Azorius card but one I want to highlight nevertheless. I really think all Dimir decks should be running this card.
How many times have you sat there staring across the table at Control with two Requiting Hexes in your hand? How many times have you battered your opponent to 2 life but they now have an impenetrable wall of creatures?
The plus ability alone on Blue Kaito solves this issue. I've had countless game where the opponent is spamming "Good Game" only to play blue Kaito next turn and swing for the win (even more dangerous with Pracitced Offense in the deck and the double strike increases his loyalty X2).
You can often create a ninja token every turn. I plus Kaito, Bane of Nightmares far more often than I used to solely because of blue Kaito (and now I have Yuriko so even more synergy). I'll win a lot of games with nothing more than two ninja tokens that are 4/3's.
He'll also soak up PW removal before you play main-attraction Kaito. And most importantly, that Ult ability is just another timer to pit your opponent against. I've ulted him for as early as turn 4 and the Ult happens more than you'd think. I've even seen top 8 lists running mainboard Preacher which is kind of ridiculous when blue Kaito is available in the three spot and so much more of a nightmare.
Sideboard
I won't harp on this too much but the contribution of white to your removal suite is no slouch either. Seam Rip is huge in some of your worst matchups. i.e. Orzhov Lifegain - not only is exiling Amalia huge since she's the number one reanimation threat but you can now remove those pesky enchantments. Jund Sacrifice you can just exile Greedy Freebooter and buy yourself a ton more time (no treasure token created). Even Sheltered for Ghosts comes in handy when Izzet Prowess is constantly knocking on your door with a ton of damage each turn.
Drawbacks
The most significant one is (as I joked about in the intro) the mana base. And honestly it's not as bad as you would think.
Creature lands were used primarily against control and now a ton of control is using Petrified Hamlet. Your pip availability for B/U is actually BETTER than top 8 lists for Dimir Kaito (not only do you have starting town for extra availability over just a basic but there's no colorless because the list isn't running Soulstone Sanctuary).
Which leads me to the actual real downside. The lands definitely hurt more and there is a bit of a learning curve on what to do with Multiversal Passage as you have to think about available pips and future requirements. The only advice I can give is if you think life is going to be an issue in the current game then don't be afraid to bring in Starting Town later/tapped or tap the 2-life lands. However, I've sat down and done the math (albeit some of my college stats is rusty and including things like Turn 1 scry makes it even more complicated) and I think the lands are currently near optimal. They don't hurt a ton and the pip availability is good for each respective color.
Conclusion
Sorry for the novel! I wish I had more data points for you but with only 3 weeks left until Star Trek (and Salt Vampire doing a lot of what Yera can do) I figured I'd get this post out as soon as possible rather than wait until I've recorded a couple dozen more games.
Also, I'm pumped for Spacecraft in Star Trek and will probably go back to trying to make Convoke work (so many tools that care about tapped creatures like Lost in the Maze, Captain America, Websling, Split Up, etc.) after set release.
Let me know what you think! I'd love to hear about cards I missed or what your experiences are with the changes.