Sultai Shardless, Sultai Delver, Sultai Control, 4c Midrange, 4c Delver are all decks that exploit those two cards effectively, but some do it better than others.
Reid Duke won GP Louisville with his own brew, and it’s been slowly displacing Sultai Shardless ever since. The reason is that Leovold, Emissary of Trest is often just better than Shardless Agent, and you don’t have to play sub-optimal cards like Ancestral Vision to get your card advantage.
I also felt that the format sped up a lot more—Fatal Push brought more Delver decks into the fold, and you also see a lot more Stifle than you used to, making 3- and 4-drops harder to cast without Deathrite Shaman or Noble Hierarch.
While I like the base concept of having 8 mana accelerants and 6 great 3-drops, Reid’s deck is weaker against combo decks than Sultai Delver, and 4 Noble Hierarchs make your topdecks weaker with fewer Ponders and more lands.
That leads me to the conclusion that Sultai Delver is now the best home for Leovold, Emissary of Trest, which might be one of the best cards in Legacy.
While Tarmogoyf is the most powerful 2-drop we have, it's weak to Fatal Push, and True-Name Nemesis is a real beating in this format with fewer combo decks and more aggressive decks.
Another card I love with all these Sultai decks around is Umezawa’s Jitte, a powerhouse with True-Name Nemesis and almost an auto-win against Death and Taxes. I really like that Reid exploited the Nemesis plus Jitte plan and I would like to carry that over to Sultai Delver.
After trying a few versions, this is where I landed:
I chose to play only 25 instants and sorceries because I wanted to find a space for a main-deck Umezawa’s Jitte. This makes Delver of Secrets less likely to flip—mostly after sideboard where you bring in Baleful Strix, artifacts, and enchantments—but there’s no shame in playing Brainstorm in your upkeep. Your hand often has the right number of lands and spells, and shuffling back only 1 card is reasonable. Making sure Delver flips is the most important thing, especially against combo decks.
In the end, I chose to cut a land and went down to 19 lands. I felt that Sultai Delver was the Delver variant that flooded most often, but it’s also the one that plays a more midrange game plan, mostly post-sideboard. I chose to cut a Wasteland—in a world of Leovold, Emissary of Trest, you don’t want Wasteland as often as you used to.
As always, you can build your sideboard from a pool of hundreds of cards, so I won't go too deep on my specific 15, but I will share my plan.
This matchup isn’t fantastic. I’d say that you are the underdog game 1 and even or a slight favorite game 2.
I’m a fan of boarding out Wasteland vs. Miracles. You beat them with card advantage, so you can't afford to draw too many lands. They will naturally go for basics, first because they fear Wasteland, and second because they have Blood Moon/Back to Basics, so keep that in mind.
Death and Taxes
This is another very close matchup where True-Name Nemesis really shines and can take over the game with Umezawa’s Jitte. I chose to cut all the countermagic, because between Aether Vial and Cavern of Souls, it's likely to rot in your hand.
The same goes for Hymn to Tourach. I thought that Hymn was bad on the draw because you were usually behind and didn’t have time to attack their hand, but the post-sideboard games are way more controlling, so you have time to do that.