A snake in the grass
Yuan-ti are serpent-like humanoids. They are the remnants of an ancient and decadent human society that engaged in profane and cannibalistic rituals to merge their forms with that of snakes. From this unholy union, different forms of yuan-ti were produced, some taking on more snake-like features while others having less. The more prominent the serpentine attributes, the higher position within the caste system the individual occupies while those who’s serpentine features are less prominent, occupy a lower position within this system, often as a spy in foreign lands.
Yuan-ti reproduce in the typical manner of other humanoids, but rather than giving birth, a female will lay a clutch of eggs. Typically, the offspring of Yuan-ti will appear as the variant of the weaker form in the couple so most Yuan-ti tend to reproduce with those of the same variant as themselves to sustain royal bloodlines. For this same reason, Yuan-ti will generally not mate with other humanoids unless required to seduce a humanoid as part of infiltrating a society. On top of this, Yuan-ti view humans the same way we view apes; as unevolved and inferior.
The different variations of Yuan-ti are:
Anathemas are extremely rare in Yuan-ti society. They appear as abominations do but with clawed hands and 6 snake heads sprouting from the body. Anathemas are formed from a ritual that transforms an abomination into a more powerful and intelligent version of itself.
The Yuan-ti view Anathemas as demigods. The presence of one in a society often drives the Yuan-ti to become more warlike, ambitious and expansionistic. They often use cults and other agents to promote their agenda within a region, taking advantage of natural conflicts until they’re able to establish themselves as rulers of the region.
Abominations are usually the leaders of a Yuan-ti society (unless an anathema exists among them). They appear as large, upright serpents, but with human-like arms that can carry tools and weapons. It is considered to be the optimal form by most Yuan-ti and one to be desired.
Malisons have a snake-like lower body and hind-quarters but a human-like upper body and head. Their form is considered imperfect in the sense that it is not the complete stage of evolution that their gods envisioned. They often fill the role of priests and other clerical leaders, seeking how they can become closer to the ideal envisioned by their gods.
Purebloods are the most common form of Yuan-ti. They appear mostly human like but with 1 or 2 snake-like features such as slitted eyes or patches of scales.
Purebloods are treated fairly, though the needs of more superior variants are considered of greater importance than that of purebloods. Typically, because purebloods look so similar to humans, they’re used as agents and spies in other nations. In this responsibility, they often wield power and luxury in their human station making some resentful to return home to their position of lower status.
Broodguards are humanoids that have been fed a special elixir that gives them scaly skin and a compulsion to follow orders at the expense of their intellect. Because of their intellectual incapability, they tend to be less capable at certain tasks than captives, but occupy a higher status due to their unwavering loyalty.
All Yuan-ti societies are built on the back of captives who act as labour for a society. All captives, no matter their race, are considered inferior to Yuan-ti and as such, have no station and are always subservient. Captives that fail to follow orders are either killed or turned into broodguard.
The unemotional, detached and arrogant nature of the Yuan-ti doesn’t lend itself towards fervent or devout worship, but the Yuan-ti do have a pantheon of gods that they worship. The 3 main gods are Dendar, Merrshaulk and Sseth, though they worship about a dozen other lesser gods along with heroes, demon Lords and other powerful creatures. Usually, these lesser gods are worshipped by individual cities or cults.
Dendar is a harbinger of the end of all things. Some believe that when she amasses enough power that she will consume the world or tear down the doors of the underworld and consume the sun, plunging the world into darkness.
Devotees of Dendar honour her through acts of terror that bring her greater power. Rather than killing those they defeat, they prefer to capture and torture them.
Maerrshaulk’s state has mirrored that of Yuan-ti society with the height of Yuan-ti society coinciding with Merrshaulk’s greatest powers while at the point at which Yuan-ti went into hiding led to Merrshaulk taking on a dormant state. Many believe this is due to the reduction in worship, though many devotees of Merrshaulk sense that his rise is close and that defeating his enemies will cause him to arise from his dormant state.
Sseth takes on the appearance of a winged Yuan-ti. He appeared shortly before the downfall of the Yuan-ti promising to bring them from the brink of defeat and back to prosperity. Many worshippers of Merrshaulk were enamoured by Sseth’s promise and switched allegiances. However, when the downfall of the Yuan-ti did occur, Sseth retreated into a dormant state, awaiting the right time to emerge and lead the Yuan-ti to victory once again.
Mind-Whisperers are the priests of Sseth who promote him by offering alternative choices to contested points of view. This brings with them an air of self-importance leading to them being disliked by others in Yuan-ti society.
Yuan-ti are vicious warriors and a cold society that make great enemies and characters alike for D&D adventures. If you want to use them in your campaign, you can find out more about them and their stats in Volo’s Guide to Monsters.