Snake Mountain is a location in the He-Man series, located on the planet of Eternia. It is located on the Dark Hemisphere of Eternia and is home to the villainous, skull-faced Skeletor. It is later revealed to have once been home to the Snake Men. Its defining feature is its snake-like shape, hence the name.
In the past, when the Horde invaded and dominated Eternia, the resident snake men were expelled the place, and the Snake Mountain was offered to the new Horde officer, Hordak, as base of the Horde for many years. Keldor, an ambitious mercenary of the Gar species, joined Hordak as his first servant, in the battle with King Randor, who deformed his face, Hordak used the Horde's powerful science to sculpt Keldor as Skeletor, training him in magic as a student. Cheating Hordak, Skeletor helped the Eternian to expel the Horde and Hordak from Eternia, then took possession on the throne of the Snake Mountain.
Snake Mountain was not introduced until some way into the MOTU franchise. Previously, Skeletor's hideout had been described as "amongst the catacombs deep under Eternia", while the bible for the Filmation series listed his base as being Point Dread, located in the middle of the ocean.
The exact age of Snake Mountain is unclear, although in the season 1 episode "Golden Disks of Knowledge" we learn that Skeletor built Snake Mountain with wisdom he learned from the Golden Disks of Knowledge, which he stole from Zanthor, a member of the Council of the Wise.
The episode "Masks of Power" reveals that many centuries ago, the Sword of the Ancients was thrust into a boulder of pure quartz, deep beneath Snake Mountain, and forgotten. According to the Sorceress, it is the most powerful weapon on Eternia, next to He-Man's Sword of Power.
The She-Ra: Princess of Power spin-off series reveals in the episode "Reunions" that during the invasion of Hordak & the Evil Horde, Snake Mountain was used as a Horde base. Eventually the Evil Horde was defeated by the Eternians. Skeletor, who at the time was a member of the Horde and a pupil of Hordak, betrayed Hordak, forcing the Horde leader to flee Eternia and abandon Snake Mountain.
Skeletor would then take Snake Mountain and assemble a roster of evil warriors for his own evil purposes.
UK Masters of the Universe comic
In issue 22, The Secret Files of Scrollos attempted to explain why the Snake Mountain playset differed from its cartoon counterpart.
Snake Mountain was formed long ago, during the war against the Snake Men. The Council of Elders used their power to bind Serpos, mighty serpent god of the Snake Men, to a mountain on Eternia's Dark Hemisphere and turned it to stone.
At first, it was a image of Serpos, with three heads like the snake god, but during the time, two heads disappeared, leaving only one and the body somewhat damaged.
During modern times, Skeletor took Snake Mountain for his own evil purposes. It was briefly taken over by the Snake Men after the release of King Hiss, but abandoned it after the presumed dead of Hiss. Skeletor remained on Snake Mountain till Hiss managed to revive Serpos. This included some kind of "regeneration", the lost two heads grew back and the whole creature began to wreak havoc on Eternia, until it was again made to stone, like in the past!
The 1980s toy version of Snake Mountain looks little like its Filmation appearance. It is a purple mountain, with its most notable feature being a demon-like face on one side. There is a trapdoor inside the gate, which is operated by a switch underneath. The toy also included a removable echo microphone, with the head of a wolf near the top. The microphone stored inside the toy, with the head of the wolf showing out the right side of the mountain. The demon face also had a lever located on the inside of the castle which allowed the user to operate the mouth of the face. This action, combined with a user speaking into the echo microphone, gave the appearance that Snake Mountain was talking in a frightening voice. A large green snake on a swivel sat near the top of the playset as well.
Snake Mountain made several appearances in the minicomics. Its depiction varies, but it tends to include both elements of the Filmation series as well as the appearance of the toy.
1987 Live Action Film
Although it did not appear in the film, Snake Mountain is mentioned at least once. Gwildor refers to Skeletor as the "Lord of Snake Mountain", which indicates that the location exists in the universe of the film.