Ras Nsi

Lurking in the heart of the Royal Palace in the ⁠Forbidden City of Omu is Ras Nsi, a mythic, villainous figure among Chultans. Ras Nsi was a human paladin and a sworn protector of the city of Mezro. He betrayed his oaths and was banished. Rather than redeem himself, he raised an undead army to conquer Mezro. The would-be tyrant was defeated and banished once more. Mezro was later destroyed by the Spellplague (or so it seemed), during which Ras Nsi lost his power to create and command undead.

Ras Nsi withdrew to the city of Omu, leaving the vestiges of his undead army to roam unchecked throughout the jungle. That was not the end of Ras Nsi, however. Bitter over his loss of power, he forged an alliance with the yuan-ti lurking in the ruins of Omu and underwent a ritual of transformation, becoming a yuan-ti malison. As a yuan-ti, Ras Nsi imposed his terrible will on the evil snake people and became their leader.