This deck plays for the long game. It is nearly always in the control role.

 Almost any hand with an Inquisition of Kozilek or Thoughtseize and 2-3 lands is keepable. Beyond that, you're usually looking for a Blood Moon or Liliana of the Veil and some number of spot removal spells.

 Demigods, Kalitas, and Hazorets are the primary win conditions, with Chandras and Lilianas as support; all of which are backed up by spot removal and discard.

Alternate Walker/Prison version here.

Update with Modern Horizons:
-2 Kalitas, +2 Endling (a better endgame attacker; resilient and aggressive)

-2 Swamp, +2 Polluted Delta (for consistency)

Considering +3 Lightning Skelemental and -2 Koth of the Hammer -1 Anger of the Gods for a more aggressive build, but it will need testing.

Turn one discard is nearly always a must, as it sets up the game for you. It allows you to take a few extra turns to build your mana before the opponent establishes a board that you have to contend with.

 A turn three Blood Moon is very powerful against most decks - and against some, induces a scoop.

 Beyond that, spot removal  keeps the game stable so you can get to the mid game.

Here's where the deck starts to shine.

 Liliana of the Veil helps establish control via discard, while playing backup to the spot removal for tough to remove creatures.

 Chandra and Kolaghan's Command introduce card advantage, while Anger of the Gods can reset if you fell behind.

 This is where we can start to introduce pressure on the opponent with Kalitas and Hazoret.

Once the board is relatively under control, and the opponent is (at least nearly) empty handed, we can start pressing the advantage.

 By this point, we often want to be close to empty handed ourselves to support Hazoret. This can be a problem in some matchups where our spot removal is less applicable. Hazoret's discard ability can be an out to a bloated hand.

 Demigod is our go-to for closing out the game. Don't rely on the reanimate ability - that's not the point, though it can be an exciting bonus. A 5/x evasive haste creature is more than worth the 5 mana investment, and it doesn't usually matter if it takes two or three turns to close the game.

 Don't forget that opponents may misplay when countering a Demigod: if it is countered before the cast trigger resolves, it will reanimate itself.

As far as matchups go, our primary nemesis is Tron (almost any variant). The quality of threat they can play early puts us so far behind that even maindeck Blood Moon and Dreadbore don't quite even the odds. The primary game plan against Tron is to avoid seeing it...

 Overall, our best matchups are Midrange and Control, where we have time to build our manabase and can make use of the variety of removal and discard. Swarm-type aggro, like certain Elves variants, can be hard to keep up with game one.

 The sideboard is a template that covers some situations I've struggled with. The Collective Brutalities are for the Burn-type matchups. Rakdos Charms are for swarm decks (but potentially could be replaced with Plague Engineer), and along with the Relic help with dredge based decks. Karn, the Great Creator + Mycosynth Lattice can be a cute trick to bring in for slower matchups. Infernal Reckoning might shore up the Tron matchup.