Purebloods form the lowest caste of yuan-ti society. They closely resemble humans, yet a pureblood can’t pass for human under close scrutiny because there’s always some hint of its true nature, such as scaly patches of skin, serpentine eyes, pointed teeth, or a forked tongue. Wearing cloaks and cowls, they masquerade as humans and infiltrate civilized lands to gather information, kidnap prisoners for interrogation and sacrifice, and trade with anyone who has something that can further their myriad plots.   Forsaken Humanity. The yuan-ti were once humans who thrived in the earliest days of civilization and worshiped serpents as totem animals. They lauded the serpent’s sinuous flexibility, its calculated poise, and its deadly strike. Their advanced philosophy taught the virtue of detachment from emotion and of clear, focused thought.   Yuan-ti culture was among the richest in the mortal world. Their warriors were legendary, their empires always expanding. Yuan-ti temples stood at the centers of ancient metropolises, reaching ever higher in prayer to the gods they longed to emulate. In time, the serpent gods heard those prayers, their sibilant voices responding from the darkness as they told the yuan-ti what they must do. The yuan-ti religion grew more fanatical in its devotion. Cults bound themselves to the worship of the serpent gods and imitated their ways, indulging in cannibalism and humanoid sacrifice. Through foul sorcery, the yuan-ti bred with snakes, utterly sacrificing their humanity to become like the serpent gods in form, as well as in thought and emotion.   Serpent Kings of Fallen Empires. The yuan-ti view their physical transformation as a transcendent moment for their race, allowing them to shed their frail humanity like dead skin. Those that did not transform eventually became slaves or food for the blessed of the serpent gods. The yuan-ti empires withered or were defeated by those who fought against their cannibalism and slavery, and the serpent folk were left in the ruins of their great capitals, far removed from other races.   Cold of Heart. Humanoid emotions are foreign to most yuan-ti, which understand sentiment only as an exploitable weakness. A yuan-ti views the world and the events of its own life with such extreme pragmatism that it is nearly impossible to manipulate, influence, or control by nonmagical means, even as it seeks to control other creatures through terror, pleasure, and awe.   Yuan-ti know that the world they hope to rule can’t be bound for long by brute force, and that many creatures will refuse to serve. As a result, yuan-ti first influence other creatures with the promise of wealth and power. Time and again, humanoid cultures make the fatal mistake of trusting the yuan-ti. They forget that a yuan-ti that acts honorably or lends aid in a time of trouble does so only as part of a grander design.   Yuan-ti leaders are cunning and ruthless tacticians who readily sacrifice lesser yuan-ti if potential victory justifies such losses. They have no sense of honorable combat and strike first in decisive ambush if they can.   False Worship. Yuan-ti life revolves around their temples, yet yuan-ti don’t love the gods they worship. Instead, they see worship as a means to attain power. A yuan-ti believes an individual who attains enough power can devour and replace one of the yuan-ti gods. The yuan-ti strive for ascension and are willing to commit the darkest atrocities to achieve it.