Yuan-Ti

An ancient people and cult-like empire long since vanished, the ruins of the Yuan-Ti are passed by many throughout the continent without so much as a second thought. If only they knew the terrible acts that took place in those ruins, and of the mortal lives that were given up in sick rituals to a depraved faith. The Yuan-Ti are believed by sages to have not come from Karthica, but from another place; perhaps from beyond the horizon and across the sea. They came as a predator would come upon its prey. Karthica was but a husk, civilisation destroyed in the aftermath of the War for Heaven and the disapperance of the Gods. The lost folk that remained were easy to enslave. Those who showed potential were exposed to the Yuan-Ti's power, to a sliver of the godly power they wielded. The embers transformed them into hybrids, or worse - abominations. It was no gift. They were only easier to control, with their loyalty assured. Those who had nothing but labour to give, or worse than this, were sacrificed in the invader's name. Their blood sustained their masters, robbing them of all hope of freedom.
  These snake-headed people enslaved the people of the continent by the tens of thousands as back breaking labour built new colonies, temples, cities... all for the invader's majesty and haughty pride. Their own gods had been left behind in their homeland. They came with a new belief; that they themselves were superior to that which had given them life. And they wielded a power described in what texts remain as 'embers' that made such a claim a reality. For almost hundreds of years, they ruled swaths of Karthica without oppostion.
  How they came to fall is lost to time. Some say it was dragons as they began to awaken and eye the world of men, elves and dwarves with greedy eyes. Others say the Yuan-Ti's gods crossed the sea after them to tear them down from their hubris and defiance. Nevetheless, the serpent god kings of time lost are one. All the same, many are unable to shake the eerie feeling they get when exploring these ruins... or the tales of folk gone missing where the remains of the Yuan-Ti's fallen temples and cities lie in cold silence.