Tainted one

Tainted ones were humanoids who had been transformed into yuan-ti servitors.

Description
Tainted ones appeared as they had prior to their transformation, and seemed normal and healthy. This meant that they could easily blend back into civilization.

Personality
Tainted ones were generally faithful servants of the yuan-ti who created them, although they had the capacity to betray their masters and strike out on their own. They often developed slightly unnerving habits, such as hissing slightly as they spoke, keeping large reptiles as pets, or frequently licking their lips.

Abilities
The transformation bestowed tainted ones with greater stamina and with psionic abilities which allowed them to inflict poison on their enemies and to polymorph themselves into snakes or snake-like creatures. They further gained keener senses and greater physical and mental fortitude, rendering them unaffected by spells designed to control them, such as hold person or charm.

The salivia of a tained one also became highly toxic when mixed with blood. This had the effect of making even their kiss potentially debilitating. Tainted ones were, of course, immune to the effects of their own poison, and likewise were immune to all types of snake venom.

Combat
Tainted ones retained the combat skills they posessed prior to their transformation. While they could use their venomous saliva to their advantage in the form of a bite, this was generally not a very useful tactic as it required close contact and access to exposed skin.

Society
Tainted ones primarily served as spies in human cities. They were also often used by their pureblood yuan-ti masters as bodyguards and as stealthy strike forces within human settlements.

Tainted ones who outlived their usefulness were abandoned by their masters, becoming free to make their own life choices. These individuals&mdash;as well as those who betrayed their masters&mdash;often sought to make livings among the underbellies of human civilizations as illicit merchants specializing in selling slaves, poisons, or ill-gotten goods to various yuan-ti buyers. Some pursued this lifestyle with the goal of earning enough money to purchase restorative magic to return them to their former selves.

Creation
The process of creating a tainted one generally involved having a human drink a special concoction brewed from yuan-ti venom and a specific mix of herbs and roots. Such human subjects were most often prisoners, but some cultists dedicated to the yuan-ti would participate voluntarily. Most&mdash;but not all&mdash;nonhumans who consumed this mixture became violently ill, and ran the risk of dying within 30 seconds. Meanwhile, humans also ran the risk of lapsing into a coma and dying within an hour, but if they survived, they then began a painful, days-long transformation into a tained one. Yuan-ti were known to revive humans who seemed poised to die from the concoction, only to force them to drink it once more and try again. However, even if the transformation began, it too could fail, in which case the subject became a broodguard after about a tenday, give or take a few days.

The transition could be reversed using magic. After drinking the potion, the transformation could be prevented if the following spells were cast in this order: neutralize poison, dispel magic, remove curse, and heal. If successful, the process was halted and reversed, although the individual's intelligence was permanently damaged. Only a wish or miracle spell was able to return a tainted one to its original form after the transformation had taken effect.

History
The process for creating tainted ones was invented by the yuan-ti of the Serpent Hills, and as of 1372 DR, it remained a closely guarded secret.  However, it was considered only a matter of time before the yuan-ti of Chult and Hlondeth acquired the knowledge as well.

In the mid-to-late 14 century DR, tained one slaves could be bought from a slaver named Zstulkk Ssarmn in Skullport.