I have been playing this version of the Mono U devotion deck. I am playing this version primarily to improve the control matchup post board as in my experience the control matchup is by far the hardest matchup for Mono U. Post board with this black splash, the deck is very favored because most of the threats does not die to verdict and has to be detention sphered or countered.
I really like it also due to the black splash upgrading my removal against green based creature decks and also by pass the blue protection creatures. In addition Thoughtseize usually replaces what used to be counterspells.
Matchups:
R/G Monsters - As usual, this matchup should be favorable for any version of mono u devotion unless the opponent has a super nut draw. This version allows you to improve your kill spells and sometimes sideboarding thoughtseize to be able to have better picture of the path of winning the game. Tidebinder Mages, Ultimate price, and Doom Blade are the key cards.
Mono B - Not much has been changed from mono U with this version except Dark Betrayals and Ultimate Price are upgrades to Rapid Hybridization. I have been sideboarding out the domestication as most mono b is going toward lifebane zombie which is not big of a problem for us. Key cards are all the one-drops, dark betrayal, ultimate price and bident of thassa.
Mono U - Against the non splash mono U match up, this deck might have gotten weaker as it will be slightly slower due to the temples and shocklands. In addition not having counterspells post board and only have 2 domestication when some mono U list might have up to 3 or 4 domestication post board makes it less advantageous. I have not had been having too much trouble as mono U's popularity have waned. Doom Blade and Ultimate Price are the key cards here but they do not hit nightveil specters.
UWx Control - This matchup has become from very unfavorable pre board to very favorable postboard. Ashiok, Thoughtseize, big Jace, Phenax, all comes in during this matchup. Most matchups will end up the UWx Control not being able to keep up at the number of diverse threats on the board that require a very specific answer. Usually in this matchup, when using thoughtseize, i hardly ever use it to take sphinx's revelation. Most of the time it will either be their win con Aetherling, Detention Sphere, or a counter spell. Detention Sphere and counterspells are the things that can ruin your game. Supreme verdicts is usually too expensive of a spell for them to kill one of your two drops, which is a good thing. if they managed to chain revelations, Phenax or Memory Adept will help you by milling out their deck. Ashiok is one of the key cards in this match up so usually I will try to resolve her last as if she does not get answered and ultimates, it is game over for the control player.
BW Control/Midrange - This deck is very similar to Mono Black and it has always had a favorable matchup for Mono U since Theros due to the deck becoming weaker without Grey Merchant of Asphodel. This matchup should be played very similarly like the Mono B matchup but easier. The only thing that can mess you up is if they play a whip, but they usually sideboard those out against you. And you will need to keep your dark betrayals for Obzeidat. I will also sometimes sideboard in thoughtseize in these matchups.
