I will be upfront about the fact that Grixis is a bit of a pet color combination for me, and while this may not be the best deck in Vintage right now (cough Shops cough) I think that Grixis Thieves is among the most fun to play.
The namesake cards of this deck are Notion Thief and Dack Fayden (colloquially known as "The Greatest Thief in the Multiverse"). The ultimate value play is to have both in play, and plus Dack targeting your opponent, making them discard two cards while you draw two! How can your opponent compete against such value. Notion Thief is probably the weakest card in the deck, but we have to stay in the flavor of Grixis thieves, so we are not going to cut them. There are some other neat interactions with Notion Thief and planeswalkers, and especially when you flash one into play in response to an Ancestral Recall. In addition to these two cards, we also have Jace, the Mind Sculptor because if youre going to play fair blue deck, you ought to play Jace, he is just too good.
This version of Grixis Thieves is built around generating value and then finding Time Vault + Voltaic Key to let you take as many turns as your heart desires (or until your opponent concedes). There are other versions of this deck that just build card advantage to out-value your opponent, but where is the fun in that? I am also including a one of Blightsteel Colossus that can sometimes act as a win button given that our deck plays Tinker.
Like any self respecting Vintage deck, we play a fair amount of mana acceleration: Black Lotus and on-color Moxen are typical includes for a blue deck, but we are going all out. Sol Ring, Mana crypt and the off-color Moxen are helping to accelerate an early Tinker.
As you will soon learn in these future deck techs that we are doing, if you are playing blue, there are a fair amount of cards that just get into your deck, regardless of how you are trying to win.
The first of these are the busted cantrips, cards that let you dig through your deck at a rate that just is not reasonable: Ancestral Recall, Brainstorm, Ponder, Dig Through Time, and Treasure Cruise all count here. Gitaxian Probe is also in this deck list, but it is certainly not a mandatory include. Time walk does not quite count as a cantrip (though you could think of it as one), but it can often get you that crucial extra turn that can let you win the game. Force of Will is a necessity for any blue deck trying to play fair Magic in Vintage (okay, as fair as Vintage gets).
In addition to Force of Will, we are going to need some more counterspells for the other degenerate stuff people are trying to do in Vintage. This is where Mental Misstep and Pyroblast come in, allowing you to efficiently answer you are opponents cards.
I also have a fair bit of Tutors in this deck, to let you get these broken cards: Demonic Tutor and Vampiric Tutor get you any card in the deck, and Mystical Tutor will find you almost anything you will need. Tinker would also count as one of the Tutors you should include in your Grixis Thieves list.
The mana base is fairly simple past the artifact acceleration. While the technically correct fetchland split would have Scalding Tarn over Flooded Strand, we are playing Vintage here, we might as well keep our fetchlands within Onslaught so we can keep the old border. We are however playing both Library of Alexandria and Strip Mine to be as greedy as possible. Strip Mine can be great to ruin someones mana and give you the occasional free win, while Library of Alexandria can break blue mirrors wildly in your favor with all the card advantage you can get. With all of our artifact mana, were also playing Tolarian Academy, because sometimes tapping one land for four blue mana can be good for a deck trying to cast 3 and 4 drops.
The final few cards in the mainboard should be pretty easy to consider flex slots, theres nothing saying you have to have these cards in here, but I think they are good enough to include. Yagmoths Will can be an amazingly broken card built for comboing off, but here its simply a value card because sometimes getting to cast Black Lotus, Ancestral Recall and a fetchland is worth 3 mana. Toxic Deluge functions as a good piece of mainboard hate against a lot of decks in the format. Shops can lose their whole board with a Deluge for 3, and Delver/Mentor decks are no different. Deluge can even be useful against Dredge if their start is not too explosive. By Force is a concession to the fact that Shops is the best and most popular deck in the format, and this card in the main deck gains a bunch of percentage points in pre-boarded games.
Finally we have the sideboard. Energy Flux is to help our storm matchup; these slots are not set at Energy Flux and could easily be replaced with Flusterstorm or Mindbreak Trap, I choose Energy Flux here because most storm decks are ignoring these kind of effects in favor of counterspells. Grafdiggers Cage is great tech against both Oath and Dredge, forcing them to play fair Magic with you. Hurkyls Recall is another card for Shops, but could easily be moved around for something else if you expect something else in your meta. Leyline of the Void is more Dredge hate. Now, some of you who havent played a lot of Vintage might say Dont you think 7 dedicated sideboard cards is a bit much for one deck? Well, yes but Dredge is an incredibly powerful strategy and most experienced Vintage players agree that it is either 6-8 dredge hate cards or 0, abandoning the matchup altogether. Lightning Bolt is a good card that could easily be replaced here by another card that you feel might make more of a punch. Mountain is a card you bring in against decks with Wastelands or other land destruction effects. We have got a lot of 4 drops, and we want to be able to cast them. Toxic Deluge is here to help the same matches as the main deck copy.
