This decklist was featured on www.MTG.one as part of a primer and sideboard guide for the Modern UB Mill archetype.
https://mtg.one/modern-ub-mill-primer/
You can look at the primer for the detailed breakdown of the maindeck and all that, but here's the sideboard discussion.
Ceremonious Rejection With a huge surge in Eldrazi and traditional tron decks, Ceremonious Rejection is very powerful. The main reason I dont run more, and sometimes dont run any, is that tron decks are such a good matchup, I rarely need many sideboard cards to fight them. Eldrazi Tron can pop off some powerful spells without tron online, hence the reason for 1x at the moment.
Extirpate for Magic Online, Extirpate is 3.47 tix (dollars) vs Surgical Extraction at 25.77 tix. I started playing with Extirpate because it was a budget alternative and quickly found that it can be much better than Surgical sometimes. Casting an uncounterable Surgical is one thing, but being able to do it at split second means youre stopping cards like Snapcaster Mage, Expedition Map, etc. This copy comes in when we want more graveyard interaction plus the added insurance of knowing it will stick.
Lilianas Defeat With Grixis Shadow falling out of favor, somewhat, Im actually thinking about cutting this all together. It primarily comes in to combat Deaths Shadow but its also randomly good against some other decks.
Pithing Needle Pithing Needle is used to combat several things: Lightning Storm, Karn, Cranial Plating/Ravager, etc. Its a very useful 1 drop that still keeps us low to the ground and efficient.Profane Momento This is most impactful vs decks like Bushwhacker Zoo, Merfolk and Affinity, but it can also gain critical life points against midrange decks like G/W Company. I generally bring these in against any deck that runs 16+ creatures.
Spell Pierce Our mainboard copy is great for the gotcha surprise, but having more copies vs control/combo decks is usually needed. Creatures usually cant kill us fast enough, especially with a bridge out, so there is a premium on countering spells.
Echoing Truth I have this as a catch all card. It works against Empty the Warrens tokens, Leyline of Sanctity, or whatever problematic non-land you need to deal with.Hurkyls Recall Affinity has been very popular lately as well as a slight resurgence in Lantern decks. While not a permanent answer, it gives us a window of opportunity to either win or stabilize. There are also random rogue decks like KCI (Krack-Clan Ironworks) and Blue Steel that Hurkyls Recall can do some strong work against.Crypt Incursion In matchups that Profane Momento come in, these come in. Its possible to not bring in momento vs burn but bringing one of these. I generally dont, as youre usually better off just racing. These are also brutal vs creature based strategies like merfolk, company, affinity, etc. Its not unusual to find yourself gaining well over 30 life.
Damnation These come in against creature heavy decks. I flirted with using Bontus Last Reckoning, but having to take a turn off is not even close to worth the cost in Modern.
Mindbreak Trap The only purpose for this card is Gifts storm. Well, that and it is one of my favorite counterspells of all time. It can also come in if youre facing something that has a combo element to it and you have to counter something (like KCI.)
Ravenous Trap While dredge is basically dead, it is still around. Living End, on the other hand, is more popular now and this Trap is a fantastic way to deal with a cast LE. If you have a Hedron Crab out, save your fetchland for your opponents turn. They may not always get three cards to hit the graveyard before you want to cast this. This trap can also come in if you happen to run into a deck playing Emrakul or any other shuffle titan, but can also blow out a storm player trying to cast Past in Flames.
Set Adrift The main purpose of Set Adrift is to handle Leyline of Sanctity, but it can also come in when youre mainboard removal is dead, like against traditional Tron. Also resolve Mesmeric Orb first post board so that your Set Adrift will only cost U.
Nihil Spellbomb Similar to Ravenous Trap, this ensures that no shuffling can happen on your watch. Its also a fine way to combat Storm or any other graveyard based deck. Using these to combat delve creatures like Tasigur or Gurmag Angler is tough because youre always trying to fill their GY, but these can come in.
Vapor Snag Before Fatal Push was printed, I used to run a playset of Vapor Snag as a way to combat big creatures like Primevil Titan and Gurmag Angler. I still think Vapor Snag is a fine tempo card, giving you that much needed turn to close things out.
