The Storm King is a satyr-like creature who appeared as the main antagonist of Lionsgate's 14th full-length animated feature film My Little Pony: The Movie. He is the tyrannical leader of the Storm Creatures and the former boss of Tempest Shadow and Grubber. He was voiced by Liev Schreiber.
He is a very campy and weak comedic villain that lacks the "comedic villain" charm, who didn't have much focus despite supposedly being the main villain. In fact, he generally lacks personality other than his goofiness. He is also not very intelligent as he foolishly betrayed Tempest Shadow, his most loyal servant, which led to his downfall.
Despite being the MAIN ANTAGONIST, he barely gets any screen time. As in, he only has two screen-time thought out the whole film. In his first on-screen appearance, the Storm King communicates with Tempest via potion spell. His second on-screen appearance is in the climax of the film, where he finally takes matters into his own hands.
His role in the movie serves more as a minor antagonist rather than the main antagonist, because his second-in-command Tempest Shadow is the one who has more screen time and drives the plot much more, therefore, Storm King does not get much development as the main villain and as a character in general. Thus, Tempest Shadow mostly does all the work for the Storm King, while the Storm King remains behind the scenes throughout most of the film.
Despite this, the secondary antagonists usually do most of the work and get more screen time than the actual main antagonist in some movies (The Original Star Wars Trilogy for example). However, this causes the Storm King to lack any development due to his limited screen time.
His betrayal of Tempest Shadow is pretty predictable and even more pointless, especially for a villain of his shtick, a ruthless monster who treats most of his villainy as a joke. Plus, it was unwise of him to flat out betray his most loyal servant, as she could have continued to pledge servitude to him if he truly did have the power to restore her horn with his staff (that's only if the Staff of Sacanas can indeed restore broken horns). His betrayal of Tempest and his attempts to kill her has led to his own downfall, as Tempest helped the Mane Six defeat him once and for all, even if it means almost sacrificing her own life.
A lot of his dialogue is a joke, as it sounds more like a child or manchild who is trying hard to be a villain.
His design, while unique, looks like a mix of Discord, another villain in the MLP franchise, and Rafiki from The Lion King, in a rather silly way.
Liev Schreiber did a decent job voicing him.
The scene where he plays with the sun and moon is hilarious.
Despite his comedic tone, along with Discord and Lord Tirek, Storm King serves as one of the biggest threats to Equestria, even putting the majority of the pony kind into slavery.
He has a pretty ruthless death scene for the movie's demographic, although there are theories that claim that his soul is still alive despite his obsidian body breaking into pieces.
There are parts where he sounds intimidating, like when he tells Tempest "Fail me, and your horn won’t be the only thing that's broken", and his breakdown at the climax.
His role in the IDW comics does the character much more justice.
Over time, the Storm King has grown a small fanbase and positive reception toward him grew, similar to King Sombra, who was initially considered a very weak villain by the fandom in his first appearance in season 3's two-part premiere "the Crystal Empire". Later on, became much more popular, and positive reception toward Sombra grew.
Andrea Libman, who voices Pinkie Pie and Fluttershy in G4 of My Little Pony, has said on Equestria Daily that the Storm King was her favorite MLP villain. Also, Liev Schreiber, along with director Jayson Thiessen, the writers, and the animators, has said that bringing the character to life was fun.
The Storm King's origins were originally going to be shown in the movie but were scrapped. It could have shown an opening sequence on how the Storm King rose to power, how he managed to conquer south of Equestria, and it would have shown his actual Storm Kingdom. It would have also explained how he got the Staff of Sacanas. Scorpan, a Gargoyle and Lord Tirek's younger brother, could have been the original owner of the Staff of Sacanas and that his staff was stolen by the Storm King with the help of the recently recruited Tempest Shadow. This could have helped the Storm King as this would have given him an interesting backstory and more character.
There have been some fans who claim that the Storm King is a rip-off of Lord Tirek. Though they do have some similarities, such as their design, the ability to steal magic, and betraying their loyal minions, the difference between them is that while Lord Tirek can absorb magic himself, the Storm King needed relics to steal magic. Plus, the Storm King is goofier than the more serious Lord Tirek.