Raise your hand if you like playing magic.
Raise your hand if you like making your opponents not play magic.
Raise your hand if you like playing your opponent's deck.
Then The Massive Betrayal is the deck for you! The ultimate goal of this deck is to control the board, ramp out some lands, and then play a Mnemonic Betrayal to cast a lot of your opponent's spells. But, in order to control the board, we need some support. So, let's look at the deck and figure out its key strategies.
Let's just get this out of the way, as this is probably the easiest part of the deck. We are running 3 Grow from the Ashes, 3 Circuitous Route, and 2 of The Immortal Sun. Grow from the Ashes is an incredibly versatile card, bringing you either 1 or 2 untapped basic lands depending if you kick it or not. Circuitous Route can fetch us the few gates we are running in the deck, but is also a great way to fetch out another two lands to thin the deck and ramp us to our final win condition. The Immortal Sun is just bonkers with Mnemonic Betrayal; by making all of our spells cost 1 less to cast, whenever we cast our opponent's spells, we'll also see the cost reduction there as well. It is a little light on the ramp cards, but we are needing to control the board more and we do have ways to capitalize on some of these spent ramp cards later.
The Control Game.
We aren't running a ton of counter control in the main deck as we are more of a tap out and go strategy. We are running a full play set of Thought Erasure and a set of 3 Disinformation Campaign. Thought Erasure is an early way to deal with what our opponent is doing by forcing them to discard key cards in their hand. We also get to Surveil 1, allowing us to fix the top of our library. Surveiling also allows us the ability to pick up our Disinformation Campaigns, an enchantment for 1UB that forces our opponent to discard a card and allowing us to draw a card, with the added clause of returning it to our hand whenever we Surveil. With our 2 The Immortal Sun, we also see some great planeswalker hate, stopping all walkers from activating abilities! This is great to shut down Teferi, Karn, Vivien Reid, Vraska, etc. Just don't forget this ability is attached to the Sun and that it affects you as well.
Along with this, we are running a fairly light suite of removal. We are running a pair of Cast Down to fight early removal and a pair of Assassin's Trophy to fight anything. We also are running 4 Discovery//Dispersal that can fill as a removal slot. Dispersal is 3UB and forces each opponent to pickup their highest converted mana cost nonland permanent and then forces them to discard a card. So, if we are running them out of resources, we can eventually return their best thing to the hand and it will go right into the yard.
The card advantage package is pretty neat. We are running 4 Discovery (the other half of Dispersal). For 1(U/B) we get to Surveil 2 and then draw a card, further plowing through the deck and finding what we need. A pair of Mission Briefing found its way
into the deck, a UU instant that allows us to Surveil 2 and then we can cast an instant or sorcery card from our graveyard by paying its mana cost. Just be aware, this does not circumvent timing restrictions for the cards you target; so sorceries are still sorceries. We've already mentioned The Immortal Sun several times now, but it also fits this slot as well. One of its many abilities is to give us an additional card draw each turn. Those resources are very important, and helps us to refuel in the late game! Search for Azcanta sees a pair here in the card advantage section. While it does mill our own library a bit, it helps fix the top of our library and when we finally flip it to Azcanta, the Sunken Ruin, we get a powerful land that allows us to dig 4 deep and will almost always give us a card.
The Win Conditions.
Finally, let's get into our win conditions. We have 2. Well, sort of.
We are running 4 Thief of Sanity and 3 Mnemonic Betrayal. Thief of Sanity, a 2/2 flyer for 1UB, will eventually win us the game if we can swing in 10 times with it. The best thing about it is its ability: whenever it damages an opponent, it allows us to look at the top 3 cards of our opponent's library and exile a card, mill the rest, and allow us to cast the exiled card at anytime we normally could by using mana of any color. This ability gives us additional resources we may lack like more removal, creatures, planeswalkers, counter spells, etc. It also fills their graveyard, further putting them off of resources, and further fueling our Betrayals.
The 3 Mnemonic Betrayals is one of the reasons we are running the ramp strategy. It allows us to exile our opponent's graveyard, and then we can cast any of those spells by paying their mana cost, treating our mana as if it were any color. So, the more mana resources we have, the more of our opponent's things we get to take. The unused cards (or the instant and sorceries we cast) do eventually go back into our opponent's graveyard, but the power is there. We basically play out opponent's deck and win with it.
The sideboard is here to flesh out our main deck a little more. I'm not worried about midrange strategies very much, I think our deck is strong against most of those in the format. Our worst match ups that I can foresee is going to be Boros or White Aggro or Counter Control. For Aggro decks we are running additional removal in an additional Assassin's Trophy, a couple Vraska's Contempt, and a pair of Ritual of Soot. I am also running 2 Price of Fames as they combo with our Disinformation Campaigns with the Surveil 2, but it is better against decks that have more legendary creatures like Niv-Mizzet, Lyra, etc. This ends up working really well as a 1 for 1 swap with Cast Down in the main deck. For counter control decks, we are running 2 Duress, 2 Negates, and 2 Sinister Sabotage. We can also bring in the Vraska's Contempts to deal with troublesome planeswalkers in addition to The Immortal Sun in the main. Vraska, Relic Seeker is in the board as an additional great win condition against do nothing decks (decks that don't have good targets for the Betrayal) or against the midrange decks that have a lot of enchantments or artifacts. It could be a decent option for going up against control decks as well as a continual bit of pressure up until you reach the ultimate for a game winning swing.
All in all, I think the deck sings. It is very control heavy on the front, then when your opponent runs out of steam you ramp into a major victory with your Mnemonic Betrayals, while utilizing Thief of Sanity as a means to sure up what you are missing in your match up. Because we aren't running a lot of creatures, if your opponents over commit to removal for dealing with the Thief of Sanity, we'll welcome the dead cards in there hand. If they under commit to the removal, we can steal the game with it. I'm loving what I'm seeing, and I think if you give it a shot, you'll enjoy it too.