Ancient king of the Snake Men, sealed away in the Void by the Council of Elders eons ago. The third major MOTU villain faction after the Evil Warriors and the Horde.
King Hsss is the ancient ruler of the Snake Men, the third great evil of Eternia after the Evil Warriors and the Horde. He was vintage 1986 Mattel canon but barely appeared on screen during the Filmation run. The 2002 MYP series fully developed him into the season-2 antagonist, with the snake-men’s escape from the Void serving as the season’s overarching threat.
The 1986 Mattel figure famously had a “snake transformation” play feature: pressing a button on the figure’s back caused his human-looking torso to retract and reveal a snake-headed second torso beneath.
Catalogue source: heman.fandom.com (CC BY-SA 3.0).