This is my relatively stock list for sultai constrictor, with a few slight adjustments to the main and sideboard. Below is a sideboard guide, and general notes on how to play the deck.
Sideboard Plans
UB Midrange+1 Vraska's Contempt+2 Carnage Tyrant+1 The Scarab God+3 Duress+2 Negate-2 Fatal Push-2 Verdurous Gearhulk-4 Walking Ballista-1 Jadelight Ranger
IF THEY HAVE GIFTED AETHERBORNE keep in 2 fatal push, don't board in negate
Mono Red+2 Cartouche of Ambition+2 Fatal Push+1 Vraska's Contempt-1 Verdurous Gearhulk-2 Bristling Hydra-1 Jadelight Ranger-1 Hadana's Climb
Grixis Midrange/Energy(Similar to UB midrange, but more removal)(Same sideboard plan, same aetherborne rule, except always keep in negates if you see walkers, and take out 1 climb/ 1 jadelight)
UB Control+3 Duress+2 Negate+2 Carnage Tyrant-2 Fatal Push-4 Walking Ballista-1 Jadelight Ranger(Unfortunately, we still need 3 contempt. It will often be a dead card, but given the fact that we just lose to the scarab god, it is a necessary evil. On the bright side, they will board in gonti, so gearhuk, scarab god, and gonti will give you 8 targets. It might be correct to just keep in 2, I'm not 100% sure.)
(UW/UR/Esper/Jeskai Gift)+2 Thrashing Brontodon+3 Duress+2 Negate+1 Scarab God-2 Fatal Push-3 Vraska's Contempt-1 Blossoming Defense-2 Walking BallistaGift has virtually no interaction, going all in on your climb "combo" can be a good plan. Board out contempts, because their non 4/4 creatures suck, and if they're reanimating, you've probably already lost. Ballista is bad mainly because it has very few targets, and I would consider taking out a third for the 2nd defense. An interesting interaction to remember is that as the gift trigger goes on the stack, you can steal creatures they would reanimate with the scarab god.
Constrictor Mirror+2 Fatal Push+2 Thrashing Brontodon+1 Vraska's Contempt+1 The Scarab God-2 Jadelight Ranger-2 Walking Ballista-1 Bristling Hydra-1 Blossoming DefenseThe mirror usually plays out in 1 of 2 ways. Most commonly, each player grinds value, trading resource for resource, until someone comes out on top. Sometimes, when one player draws very little removal, the other player can leverage this and get a fast combo kill, or an enormous amount of snake/gearhulk value.
Vampires+2 Thrashing Brontodon+2 Fatal Push+3 Duress-3 Vraska's Contempt-2 Blossoming Defense-2 Hadana's ClimbThis match is generally pretty bad. Duress is always better than defense, as it can hit radiant destiny, and most importantly, profane procession. Game 1, you need to stabilize against the early onslaught, and then you will most likely win the late game. In this type of game, you would want cartouche. However, game 2 is different. More removal, bigger threats, and profane procession demand interaction even in the late game, but the early onslaught still exists, which is why we take out climb.
Green Red MonstersThis matchup is virtually identical to the mirror. In my personal option, I view R/G as a slightly weaker, but slightly more consistent version of sultai. Well timed scarab gods, contempts, and pushes can absolutely cripple the deck. Play reactively early on, then apply pressure later on, as they can't interact with your combo. Same sideboard plan as mirror.
WG TokensVery uncommon deck, similar to vampires. Same sideboarding, except keep defenses and 1 contempt, and don't put in duress.
Mardu Vehicles+2 Thrashing Brontodon+1 Vraska's Contempt+2 Fatal Push+2 Cartouche of Ambition-2 Bristling Hydra-2 Jadelight Ranger-2 Hadana's Climb-1 Blossoming Defense
Deck Notes
The Combo Hadana's climb+hydra/gearhulk/carnage tyrantUnlike pummeler, our gameplay doesn't revolve around the combo, it's just a secondary win condition. Blossoming defense all helps push through damage with the combo.
2 Drop SelectionThe last tricky part about the deck is knowing what 2 drop to play. I play 3, and I would argue that none of them are "the best". Each are good under certain conditions, and it is important to be able to evaluate those conditions
Constrictor Constrictor is at its best when it is followed by jadelight or climb. Moreover, constrictor has the most lategame impact, so if you suspect your opponent has removal, then play something else. Generally, constrictor is your highest value 2 drop, and while other might be better in the short term, you should prioritize constrictor's survival. Also, if you have a defense in hand, play constrictor turn 3 with 1 green up. So, if you think your opponent has interaction, and you have another 2 drop, generally don't play constrictor turn 2.
Siphoner Something important to note with siphoner is that opponents will value it much higher than you will, as it plays a more important role in other black blue based midrange/control decks. Sometimes, opponents will go so far as to kill siphoner over constrictor. Use this to your advantage. Siphoner is at its very best when you play aether hub, so it can draw immediately, and generally, even without hub it is best turn 2. So, if you have a siphoner and a constrictor, typically play the siphoned turn 2. Either it eats a removal spell that would have hit constrictor, or it either immediately draws or attacks for energy.
Servant Servant is an interesting card. It is generally either your best or your worst 2 drop. If you have a hydra, then its value immediately multiplies, as you can play hydra turn 3. If your opening hand consists of servant, siphoned/constrictor, hydra, and no gearhulk, always play servant turn 2. The potential upside of hydra is high, in addition to the fact that servant will be terrible later on. If your hand consists of no hydras/gearhulks and you suspect them to have removal, play servant turn 2, as it is effectively worthless. If you have gearhulk, servant, and siphoner, play siphoner, then servant turn 3. That way, siphoner will take a removal spell, and you can play a turn 4 gearhulk. In that same scenario, if you have constrictor instead of siphoner, play servant first, as the potential upside of constrictor/gearhulk is so high.
Removal Against UB based deck, if you have 1 contempt, save it for scarab god.Against, UB, Grixis, and Red, always assume they have 1 early removal spell.
