Blue/Black Cipher (Casual)

The key card : Invisible Stalker - to play as soon as possible and cipher every spell on him.

Cipher spells :
Hands of binding is the best spell to cipher: cheap mana cost and helps to tempo the opponent
Hidden Strings is basically a free spell if you untap 2 lands and helps you get some mana available during the opponent's turn.
Last Thoughts and Mental Vapors are here to generate card adventage. Very expensive mana costs for the immediate effect, but great value over time. And it's a cipher deck, so we play spells with cipher ^^
Shadow Slice is one of kills of the deck, but is expensive and is strait card disadventage, one is enough
Stolen Identity, mostly for fun (6 ccm) but you can copy the best artifact or creature of your opponent, or your invisible stalker if that is all there is.
Undercity Plague : good value over time, but pretty slow for a 6 ccm sorcery spell.

Kills:
Shadow slice
Talrand, to get an army of 2/2 with flying
Consuming aberration : mills out the opponent

Control :
Counterspell : Helps you with any kind of threat (board wipes are the biggest danger). Counterspell is pretty overpowered in comparaison to other counter spells, but it's cheap (money and mana) and it compensate for cipher spells... ^^
Fog bank and wall of frost are good walls
Rapid hybridization is a very cheap and efficient removal
Duress : also cheap and efficient especially against planeswalkers that you cannot handle well otherwise
Tablet of the Guilds : to have some precious life gain. Like the other cards : bad when you play it but good value over time.
(Control is about adapting, so adapt if you need more/less removals/counterspells...)

Fireshrieker : To have twice more fun !

A word on the mana base:
I did it with what i had, but make sure that you have enough black sources to be able to have godd chances to play duress T1

Other cards to consider :
Call of the Nightwing instead of talrand, much slower but less fragile
Paranoid Delusions : anotherkill but very slow and does not impact the board