Khans of Tarkir is the first expansion in the Khans block of the trading card gameMagic: The Gathering, slated to be released on September 26, 2014. The pre-release event is set September 20th - 21st, 2014. It's set on the plane of Tarkir, the homeland of Planeswalker Sarkhan Vol. According to Mark Rosewater, "There is something that people have been asking us to do for quite a while that we’re finally bringing back after a long absence in Magic, and there’s something that people have been asking us to do that we have never done that for the first time we’re doing in Khans of Tarkir", meaning fetchlands getting reprinted and creating a set themed around wedges, respectively.
The set will focus on the "wedges", or sets of three colors that are rooted in one color and the two across from it. Each wedge is the colors of a clan of warriors that venerate a certain quality of the dragon and the part that goes along with that, even though dragons are extinct. The clans are as follows, and each is led by a "khan", or warlord:
The Mardu Horde (Red/White/Black) views speed as the greatest aspect, and use the wings to represent that. They are led by Zurgo Helmsmasher.
The Jeskai Way (Blue/Red/White) prefer the cunning nature of the dragon, and represent themselves with the eye. They are led by Narset.
The Temur Frontier (Green/Blue/Red) believe in the dragon's savagery, and use the claws as their symbol. They are led by Surrak Dragonclaw.
The Sultai Brood (Black/Green/Blue) make themselves ruthless like the dragon, and see the fang as its most ruthless part. They are led by Sidisi.
The Abzan Houses (White/Black/Green) see endurance as the most important quality of the dragon, and use the scales to show that. They are led by Anafenza.