Stax is a theme similar to control, where you use powerful enchantments and other effects to deplete and shut down the board. You play a lot of spells that say things like "Spells your opponents cast cost 1 more to cast", or "your opponents can't cast creature spells with converted mana cost 4 or less". At some point, your opponents won't be able to do anything. This is called a lock. These decks also play cards that effect everyone, like Thalia. The decks win con is to lock out the game and have those small points of damage add up.Some examples of good stax commanders include Zur the Enchanter, Derevi, Imperial Tactician, Atraxa, praetor's voice, Oloro, Ageless Ascetic Queen Marchesa, and Grand Arbiter Augustin IV. Powerful cards include:
Armageddon, Thalia, Guardian of Thraben, Magus of the Moon, Smoke, Overburden, Smokestack, Status, Humility, Embargo, Ghostly Prison, Propaganda, Lightmine Field, Ravages of War, Stony Silence, Back to Basics, Gin-Gitaxias, Core Augur, Vorinclex, Voice of Hunger, Winter Orb, Sphere of Resistence, Aura of Silence, Gaddock Teeg, and many more.
I recently made a Zur the Enchanter deck that uses his ability to easily cheat out tons of lock enchantments. The deck can lock down the opponents very fast.