A while ago, I experimented with a mono-blue list based around Tempest Djinn for a Pro Tour. While it ultimately didn't work out for that tournament, I enjoyed playing the deck a lot, and I hoped I'd have the chance to work more on it in the future.

Because of this, I was happy to see not one but two mono-blue decks in the Top 32 of the Magic Online PTQ, and a similar list went 5-0 in a League a couple of days later. The deck is a bit different from the one I tried originally, but a lot of the components are still there. More importantly, most of its core components will survive the approaching rotation, which makes it an interesting deck to focus on. Here are the three lists:

JakubJ's Mono-Blue

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Decklist Stats Sample Hand
Creature (20)
2 Baral, Chief of Compliance 2 Exclusion Mage 4 Merfolk Trickster 4 Siren Stormtamer 4 Slither Blade 4 Tempest Djinn
Instant (12)
1 Commit // Memory 3 Essence Scatter 2 Spell Pierce 3 Unsummon 3 Wizard's Retort
Artifact (2)
2 Aethersphere Harvester
Enchantment (4)
4 Curious Obsession
Land (22)
22 Island
60 Cards
Sideboard (15)
2 Deep Freeze 3 Diamond Mare 2 Jace, Cunning Castaway 2 Negate 4 Nimble Obstructionist 2 Surge Mare
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Negi_Negimaster's Mono-Blue

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Decklist Stats Sample Hand
Creature (19)
1 Mystic Archaeologist 2 Baral, Chief of Compliance 4 Merfolk Trickster 4 Siren Stormtamer 4 Slither Blade 4 Tempest Djinn
Instant (14)
2 Commit // Memory 3 Essence Scatter 2 Spell Pierce 3 Unsummon 4 Wizard's Retort
Artifact (1)
1 Aethersphere Harvester
Enchantment (4)
4 Curious Obsession
Land (22)
22 Island
60 Cards
Sideboard (15)
2 Aether Meltdown 3 Deep Freeze 3 Negate 3 Nimble Obstructionist 4 Syncopate
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KevinTheRelentless's Mono-Blue

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Decklist Stats Sample Hand
Creature (21)
2 Exclusion Mage 4 Merfolk Trickster 1 Mist-Cloaked Herald 4 Siren Stormtamer 4 Slither Blade 2 Spellweaver Eternal 4 Tempest Djinn
Instant (12)
1 Commit // Memory 1 Dive Down 1 Negate 2 Spell Pierce 3 Unsummon 4 Wizard's Retort
Artifact (1)
1 Aethersphere Harvester
Enchantment (4)
4 Curious Obsession
Land (22)
22 Island
60 Cards
Sideboard (15)
2 Negate 1 Aethersphere Harvester 2 Aether Meltdown 2 Baral's Expertise 2 Chart a Course 3 Nimble Obstructionist 3 Syncopate
Deal Another Hand

Historically, this type of deck has been classified as "aggro-control," since it's an aggro deck with counterspells. I think that's a bit of a misnomer, because those decks simply cannot play the control role. A control deck is happy to extend the game, and this deck desperately wants to end it. I find the classification of a "tempo" deck much more apt, both for decks like this and decks like Temur Delver in Legacy, which have the same philosophy.

This deck is not meant to win an attrition war. You don't have to deal with all their permanents. What you need to do is stick a threat in play, and then attack while you react to what they are doing. If the game is just being prolonged but you don't have a threat, then you're not accomplishing anything, and all those Unsummons and Spell Pierces will be dead in the late game.

Unsummon
Unsummon | Art by: Nils Hamm

The best threat in the deck by a lot is Tempest Djinn. On turn four, it attacks for 4 in the air, which is a very respectable amount, and it has the potential to attack for much more in the late game. If you have a Djinn out, then it's very easy to execute your "stall the game out until they die" plan. The issue is that, other than Tempest Djinn, nothing is very exciting as a threat, and most things have to be complemented in some way or another.

I'm a big fan of Baral, Chief of Compliance in lists like this, because I think it plays double duty. Not only does it make your spells cheaper, but it also loots away your extra lands and situational cards. A deck like this doesn't have many sources of card advantage, so you can't afford to have dead Spell Pierces, Essence Scatters, and Unsummons on top of that. All your cards have to count, and Baral makes sure that happens. In previous versions of this deck, I ran a lot more counterspells and I was happy with four Barals, but the newer lists don't run nearly as many, so I think two Barals is a good number.

The rest of the threats are, well, a bunch of necessary evils. You need creatures to carry your Curious Obsession (which is a great card in the deck; I really like that it brings Tempest Djinn out of Chandra, Torch of Defiance, and Glorybringer range) and to do chip damage while you deal with their threats one at a time. I don't have any strong feelings on them, other than that I don't think you should play any 1-toughness creatures besides Siren Stormtamer, because of Goblin Chainwhirler.

As far as the spells go, like all the counterspells, but I would err on the side of more Negates than Spell Pierces. I think you end up needing to counter a card like Fatal Push or Magma Spray a lot, and those are cheap enough that Spell Pierce is not effective. I still like a mix, though, as there's real value in having a diversity of this type of effect.

You also need a bounce spell of some kind, to deal with troublesome permanents. In a version with four Barals, I like Blink of an Eye, but with two or fewer, I like Unsummon.

In the sideboard, I like the Diamond Mare a lot. It's a great blocker versus red The Flame of Keld decks, ensuring you're not going to be burned out. Past that, you want a bunch of counterspells for Turbo Fog and control decks, and I think you also want a couple of Vizier of Many Faces for Carnage Tyrant out of Fog.

This is what I'd play:

PV's Mono-Blue Tempo

Download Arena Decklist
Decklist Stats Sample Hand
Creature (18)
4 Tempest Djinn 2 Baral, Chief of Compliance 4 Merfolk Trickster 4 Siren Stormtamer 4 Slither Blade
Instant (14)
1 Commit // Memory 3 Essence Scatter 1 Spell Pierce 2 Negate 3 Unsummon 4 Wizard's Retort
Artifact (2)
2 Aethersphere Harvester
Enchantment (4)
4 Curious Obsession
Land (22)
22 Island
60 Cards
Sideboard (15)
2 Negate 2 Vizier of Many Faces 4 Diamond Mare 4 Nimble Obstructionist 3 Syncopate
Deal Another Hand