If this were a different present, Tarkir would be in the clutches of five powerful khans. The deserts and the forests would be rife with bloodshed and plagued by war. The clans would be locked in battle for control of immense fortunes and vast kingdoms. But this is not that present. This present was never the khans' to rule. This present belongs to the dragons.
The mighty dragons of Tarkir owe their existence to Planeswalker Sarkhan Vol. From a dragonless present, he travelled back in time more than a thousand years to a crucial turning point, and there he saved Planeswalker Ugin, the Spirit Dragon, from death. In doing so he ensured the continuing presence of the dragon tempests, the storms that feed on Ugin's magic and birth dragons, and thus he ensured the continuing presence of dragons.
For many years, the clans had been fighting a war against the dragons for their own survival, hoping to gain some advantage in the struggle. But that hope was dashed when Sarkhan intervened. With the dragons' presence secured, draconic numbers grew and soon, the tide of the war turned. Ultimately, the dragons were able to hunt down the khans and destroy them. Then all that was left was for the dragons to claim their place on the vacant thrones.
In this present, the defeated clans are ruled by five legendary dragonlords. Over time, the clans have come to embody the predominant aspects of their draconic masters, and they represent these strengths with draconic symbols. Each clan battles with mana from an allied color pair, wielding its magic on behalf of its dragonlord in a bid to gain control of the entire plane of Tarkir.