It's basically an early 80s light fantasy adventure that introduces the ponies, their world, and a surprisingly dark villain. I don't think the franchise ever really has one like that again as he comes across as evil-evil more than cartoon-evil. Future villains have much more frivolous goals and a much lighter air to them. There's some songs (including this
infamous one) IIRC. Think it's just a two part special at that. Nothing complex, hell, maybe nothing even that special but it's definitely better than what followed.
It's not until the subsequent stuff that the merchandise machine feels like it's in full effect and I wouldn't hesitate to call it a unique outlier of the franchise.