First of all, I really like your deck. It looks a lot like where I wanted to take my pre-release deck.

I have one main problem though: I can't decide whether to run Nightveil Specter or Deathcult Rogue . The specter helps eliminate an extra card fro the opponent's deck (though the chances of being able to play it are slim), but the rogue is harder to block.

What are your thoughts on this matter?

Oona, Queen of the Fae perhaps??? heavy hitter that mills and propagates little chumps...

Also, I feel like Sleep might be better than AEtherize .

i like the 2/3 and i like the mechanic, but it isnt necessary. there is room there.

I like the instant speed of AEtherize , mid game and they are tapped for a hellkite or something, aetherize, huge swing.

I like it. Looking forward to the discussion. +1

Really liking this. +1

I think spectral flight is a bit over the board. 6 or your 13 creatures don't need it.

Also I don't get the point of supreme verdict in the main deck. Your main powers rely on creatures, in fact cipher relies on creatures not dying, not being exiled or flickered. In fact, your white colour spells can be used for counters like dissipate, dimir charm, negate, dispel and other things.

-2 Supreme Verdict , +2 Dimir Charm , and replace Terminus with Cyclonic Rift (since chances are if you need terminus they're attacking you with creatures), and you're pretty set. When would you ever need to sideboard in card:Sphinx's Revelation? It's too expensive to defend you from RDW for lifegain, and card draw isn't a sideboard thing. I'd just replace it with some more cipher spells. Detention Sphere s... okay granted d-spheres are useful and maaybe you should splash for that; it's nice to kill enchantments/walker with it but chances are the enchantment won't hurt you that much and if it does, a rift to a negate should do the trick. Creature-killing wise there's always Sever the Bloodline .

-2 Hands of Binding mainboard and replace it with something else and 'cause you can't cast it in the first place if they have no creatures, throw the other 2 hands of binding on the sideboard.

I feel like I'd want to slap Tricks of the Trade on Lazav, Dimir Mastermind and deal tons of damage and have a safe cipher target.

I know people talk about keyrunes being bad but Dimir Keyrune is also a great cipher target.

Jace's Phantasm in my opinion should not go sideboard. They're 1 cost creatures for a potential of 5/5. They're pretty much the blue Wight of Precinct Six. I don't see the potential of them being mainboard either, because your milling seems slow early game.

Throw the specters outt... they seem kinda useless, since you won't be casting enemy things anyways.

Maybe +2 Evil Twin sideboard to deal with legendary or even put them mainboard since they can copy any creature on board. Heck if you're feeling bold +2 Stolen Identity mianboard can accelerate your milling/killing and even mana ramp potential (say if you run a Dimir Keyrune or something)

I suggest you try out these cool interactions that both give 1 more free grind:

Voidwalk +Balustrade Spy = 1 free cast of grind per attack, 2 with consuming aberration.

Call of the Nightwing +Undercity Informer = okay, this needs 1 mana, but can be used at different times in different bulks. plus they can be 1/1 chump blockers that mills the opponent when they have done their job.

Nightveil Specter can, at the very least, give you some lands. I have a similar deck concept: Library Stalker, but using Bane Alley Broker instead of Last Thoughts for card draw and (ab)using Soul Ransom and card:Jace's Phantasm. You might want to consider Dimir Keyrune for control matchups, as the ciphered cards will stay attached to the keyrune, even in regular artifact form. Just makes it that much harder to remove when the board's being nuked constantly.

+1 I would sideboard Sever the Bloodline and mainboard 2x Murder or something similar.

What about Fog Bank ? To keep yourself from getting hit early on.