Legend of the Crystals is a four-episode animated sequel to the SNES game Final Fantasy V, set two centuries after the game's end. Unfortunately, since it came out years before any version of its source material reached the west, this served more as one of the two main sources of the chagrin the series received when it was released here than a selling point. (The other, much fairer criticism it often recieves is there there are far too many panty and butt shots, which is totally true.)
When it came to North America and the UK on VHS in the late 90s, people were far more likely to associate the Final Fantasy name with the magical cyberpunk aesthetic of Final Fantasy VII, rather than the mixture of european and asian fantasy, with some sci-fi elements added in for good measure that LotC has. As a result, it's mostly forgotten, and when it is remembered, it's often unfairly lumped in with other, much worse 90s videogame OAVs, like Panzer Dragoon and Psychic Force (both of which are based on excellent games, making them even more frustrating). As a result, it's never been officially released in any digital format in the west, and possibly not even in Japan.
Anyway, the story has a lot of typical fantasy OAV tropes: big airships, a dragon, an RPG-style party of adventurers, heroic ancestors and so on. The plot is pretty average RPG videogame fare too: a group of heroes are gradually drawn together by fate to save the world from a giant robot zombie space wizard. But the mistake I think a lot of people have made when appraising this series is by placing too much importance on the story and characters. They're not bad, but they're nothing particularly exciting or original. The real reason you should watch Legend of the Crystals is because it's beautiful.
The most obvious touchpoint for this is the colour palette. Off the top of my head, I can't think of another animation with such distinct and attractive colour choices. The music is great, too, from the background music that's taken up residence in small small part of my brain ever since I first watched the show about 18 years ago, to the haunting ending theme, all the music is really high quality. I could keep going on and on about how great LotC looks and sounds, and in all the different ways, but I'll stop and just tell you to go and watch it. It's been out of print for well over a decade, and before thn it was only available on VHS, so I think you can let your conscience rest easy should you choose to pirate it, and it's only 4 half-hour episodes, so it's not like it's a big time commitment, either.