The deck presented here is the first one I concocted after discovering Oathbreaker. It was not my first idea, but it was the one that sounded the most fun to play. Little did I know the monster it would become. Keep in mind, this build is the first iteration of this deck. It was built with a $225 league restriction. There are certainly improvements to be made if you increase the value cap. I’ll give suggestions as to what cards to remove and what to replace.
The deck relies on the Affinity keyword of Thoughtcast to cast it for 1 mana again and again and again as many times as needed to secure a win. Affinity reduces the casting cost of Thoughtcast, which means it helps counteract the command zone tax. With enough artifacts in play, our Signature Spell will cost a single blue mana…until someone wipes your board. The deck wins with the help of 2 cards, both doing completely different things. Let’s start with the coolest one.
This is, in my opinion, a very underrated card. Altar of the Brood not only fits the goal of playing small artifacts to generate more Servo artifacts, but also serves as one of our main win conditions. Almost every card in the deck will trigger it twice (once for the permanent itself and once for the servo our Oathbreaker produces), making for a very fast milling machine. Our deck is packing cards to help the altar do it’s thing by making MORE altars. Mirrorworks , Sculpting Steel  and Saheeli herself can provide you with a second altar, making the milling job that much more efficient. Prototype Portal  also generates a new altar every turn. (Not that you need more than 1 or 2 to win, anyway!).
I speak with experience when I say this is your main win condition. We will end up with an armada of servos, but can’t count on them attacking the turn they are created, and you most likely won’t get another turn if you get a battlefield full of servos. Attacking with 40 1/1s isn’t the way to win. We weaponize those 1/1s with the altar and kill everyone through milling.
Most of the time you will have around 5 to 8 tokens on the board before you combo off. Of course, those can certainly attack when needed. Here’s where our second win condition comes into play.
Coat of Arms is pretty self explanatory. The dozens of servos you will create on your turn will have summoning sickness, but that doesn’t matter. The ones from previous turn are now immense and will certainly bring your opponent down.
Two cards will find exceptional value in attacking:
Sword of Feast and Famine  and Storm the Vault . If you are like me and have a short attention span, you might end up using your attack step to untap your lands with the sword to create more servos and not realize you’ve already attacked when comes the time to go sideways with your 40/40 servos pumped up by the Coat of Arms. I know this sounds like a silly mistake, but be careful; it’s easy to lose track when playing this deck. After all, your “go off” turn will most likely last a while. Keep that in mind. This warning also applies to attacking to kill a pesky Planeswalker, like the infamous Narset, Parter of Veils.
There are two more topics I want to address. Next, let’s talk about some weird inclusions in the deck and why. Then, I’ll walk you through some of the changes you could make to make this list even more powerful.
Mishra’s Self Replicator  This expensive and seemingly garbage card is actually quite efficient in fringe cases. With Ashnod's Altar .This will net you a colorless mana every time you play an artifact. This card has won several games after my servos were destroyed by a Damnation .
Memory Jar  Although expensive, your cost reducers can make this free. Exiling a hand of 12 lands to draw a fresh 7 and keep your engine going is an ecstatic feeling. It’s also a good way to use all of our extra colorless mana to draw more cards.
Blinkmoth Urn  Yet another 5 mana artifact, this one is likely to be cast for the full cmc. Although inefficient at this cost, the Urn can let you go off one turn earlier with the slight mana boost on early turns. If you manage to play it on turn 4 with Etherium Sculptor  and a couple artifact lands, you might get 4 to 6 mana; more than enough to win a couple turns earlier than planned.
Tron: Urza's Mine , Urza's Tower , Urza's Power Plant . Like I said at the beginning, this build is the first iteration and I must admit I no longer have justification for including these. During deck building, I vastly underestimated the deck’s power and thought it would take much longer to combo off. I sent my decklist to my league organizer and didn’t realize those lands would be better off as islands.
Speaking of lands, you may have noticed the deck is only running 2 Mountains. Only 2 cards cost red: Storm the Vault  and Counterflux . The deck is essentially colorless, but our Signature Spell Thoughtcast  requires blue mana to cast it. Any mana that isn’t blue is far less useful. I am considering going down to a single Mountain because Path to Exile  is an auto-included in any white deck so it’s important to have at least one if we need red.
Here are some changes I recommend to the original list.
Tron Lands -> Islands (or better) If you have the budget, I would consider Minamo, School at Water’s Edge , since it’s essentially a “better island.” On the off chance you get to untap your Vault of Catlacan , you probably win on the spot.
You can also use Shelldock Isle  or any other blue land that you like, thought I would prefer ones that come into play untapped. Every mana has the potential to let us draw 2 cards, so we don’t want to miss on this additional mana each turn. To reiterate, tron lands serve almost no purpose in this deck.
Mana Rocks. I would fill the deck with better mana rocks, notably: Grim Monolith , Mox Amber , and Mox Opal . These fit our strategy perfectly. Blinkmoth Urn  is good, but it’s too expensive and does nothing the turn you play it, our deck is looking to combo off in a single turn.Additionally, although Vedalken Orrery  is a great card, it doesn’t really help our strategy and, like the urn, does almost nothing the turn we play it. Lastly, Ichor Wellspring , Mishra’s Bauble , and Tormod's Crypt  are in the deck as cheap artifacts to help fuel the rest of the deck so any of them may be replaced without too much impact. The Wellspring is my least liked. It’s usually free, but the rare case where you pay mana for it make the card feel very awkward.
I would replace Blinkmoth Urn with Grim Monolith, Vedalken Orrery with Mox Opal, and Ichor Wellspring with Mox Amber.
There’s one last change I want to propose. Counterflux  was a very weird inclusion in the build. Not only does it require red mana, but our deck very rarely keeps mana up on other player’s turns. I feel a one-of counterspell is mostly useless, as it’s rarely in your hand when you need it, and often forces you to keep mana open when you should otherwise not. If you really want a counter to protect your combo, I suggest a one mana spell like Spell Pierce  or Spell Snare . Personally, I would use this slot to include yet another cost reducing effect. Little choices remain, but Cloud Key  is still available. I had completely forgotten that this card existed and am now redeeming myself and adding it to this list.
Keep in mind that with Saheeli’s ability, copying cards does not trigger their enter-the-battlefield clause. Do not copy cards like Cloud Key , Semblance Anvil , Everflowing Chalice , or Prototype Portal .
This deck is very fun to play and feels like you’re going infinite when, in fact, you are not. None of your friends can complain about you going “infinite.” After 10 games I didn’t once need an infinite loop.
If you are going to play this Saheeli/Thoughtcast deck, play it alone, test it, goldfish it. You don’t want to be in the middle of a real game, fizzel out your combo, and realize you made a mistake. No one is going to let you live a second turn to try it again.
I hope you enjoyed this deck tech and here’s hoping you give this monster of a deck a try.
Here’s the next iteration of this deck I’m going to be using.
Im a professional Game Designer and have studied the field for many years.
When it comes to Magic, Ive been playing since Alara. Ive played modern a bit and with the advent of MTGA, I dabbled into standard to great success but Im mainly a EDH player and a seal format enthusiast.
Deck Brewing is my favorite part of the game along with the strong and amazing community.