Last time around, I profiled one of Tarkir's five clans: The masters of Speed, the lords of the Dragon's Wings, red-white-black's Mardu Horde. This is the introduction to the clan system:
The one major mechanical-slash-flavorful thing we know about Khans of Tarkir is that during the time period that the first set of the block takes place in (for this is a block that doesn't take place in a linear time fashion, as it were), the wartorn plane of Tarkir is divided up between five warring clans, each representing a "wedge" tricolor combination. Usually, this means a color and its two enemies, but for Tarkir this represents a color, one allied color, and one enemy color, for reasons that have yet to be explained (though this is the same as the usual idea in most practice).
The clans have a love-hate relationship with Dragons - having killed the species all off, they continue to revere one aspect of the great monsters, and embody that with a symbol drawn from a Dragon body part.
The Mardu are fast and unsubtle. Another of the clans is entirely the opposite of that. This is the Sultai Brood, who are centered around black but also use green and blue mana. These treacherous necromancers and murderers hide out in a steaming jungle, and true to their preferred Dragon aspect - ruthlessness - they can't even get along with each other. Their symbol is the Fang of the Dragon, puncturing their enemies to drain their vital energy.
The Sultai are led, if that is even an applicable word for the person giving orders to some of the most treacherous and self-interested individuals in the entire Multiverse, by Sidisi, a Naga queen who gained her dark powers through deals with the Rakshasa, who are a demonic race of tigerfolk, and whom she no doubt also intends to betray. The presence of Nagas and Rakshasa perhaps tips this off, but the Sultai are somewhat themed around ancient India, as one of the more (if not the most) "civilized" clans, modeled after a culture that built great cities and was known for often ruthless politics.