The yuan-ti are a race of human-snake hybrids in Dungeons & Dragons, introduced in Fiend Folio (1981). Purebloods, mostly human, serve as infiltrators and diplomats; halfbloods, mixed with snake features, act as warriors and temple aides; and the abominations, almost wholly serpentine, are the most venerated, serving as clerics. Their patron deity is Zehir.
At their core is the premise that they degenerate humans into reptilian forms over generations. A cold, alien caste of near-pure snakes ruling as priests speaks to our world’s concern with the slow corruption and transformation that turn a human, by degrees, into something else.