Yuan-ti

Yuan-ti are a race of serpentfolk who are generally seen as corrupt and degenerate monsters by other races.

Description
Jamedi Cosko described the yuan-ti as people of scale and fang, or snake-folk. He discussed variations of their strange physical forms: some have heads that are full of serpent features, patches of scales, yellow eyes, as well as some with limbs themselves transformed into snake-like forms.

Urukaxyl
A yuan-ti clan dedicated to the dark god Zehir, the Cloaked Serpent, inhabited Urukayxl and regularly fought the lizardfolk there for control of the territory.

On Urukaxyl, the yuan-ti have built a village around the Temple of the False Serpent, which was a temple to Uk'otoa until Zehir commanded his servants to seize the temple and use it as a seal to prevent Uk'otoa's return from banishment. The yuan-ti there dress in simple attire suitable for the jungle environment and shun hoods so both members of their society and trespassers are easily identifiable.

Lushgut Forest
Deep in the Lushgut Forest on the Menagerie Coast is a hidden society of yuan-ti who worship Melora rather than Zehir, but their lives are cut short by a curse that may be related to a nearby sunken temple.

Mordanr Isle
Off the coast of the Tooth of Zehir is the Mordant Isle. On the island, the ruins of Sariss, the Jade City, are home to a colony of winged yuan-ti who call themselves the Chosen of Zehir, worshiping him against any warm-blooded creature, specially the denizens of the Miskath Strand.

Trivia

 * Off the western coast of Tal'Dorei is Visa Isle, where the elite of a "serpentfolk" empire have kept themselves in stasis since before the Calamity. They are not explicitly called yuan-ti, but the ghosts of the serpentfolk look like the more serpentine-bodied types of yuan-ti, and their statblocks show similar magical abilities to those of a yuan-ti.