The most loyal followers of the dark gods, certain Yuan-ti abominations might perform a ritual that, if successful, transforms them into an even greater form: a yuan-ti anathema. This ritual demands the sacrifice of hundreds of snakes and requires the abomination to bathe in the blood of their enemies. The transformation is quick but painful.
Anathemas consider themselves demigods on the path to greater divinity. They demand obeisance from weaker creatures and use every resource at their disposal to war against neighbors, seeking the captives, sacrifices, glory, and riches the anathemas believe they need to achieve true divinity.
Anathemas don't age, allowing them to pursue their goals until the end of days. Truly powerful ones might rule multiple yuan-ti cities and bring entire regions under their control.