Just prior to his death in 1966, Walt Disney acquired the film rights to author Lloyd Alexander's childrens fantasy series, the Chronicles of Prydain, of which The Black Cauldron (Newberry Honor book, 1966) was the second volume out of five. In 1985, the Disney studio released an animated film adaptation of the book, advertised as Disney's "25th" animated feature (counting all of the package films the studio released between 1942 and 1949, but conveniently leaving out Victory Through Air Power).
The movie was the darkest animated film Disney had released in a very long time. Just prior to release, it was subjected to censor demands that certain scenes be cut (mostly those involving the film's villain, the Horned King), in order to bring the film down from a PG-13 rating to a PG rating. The final result was panned by most critics and did poorly at the box office. However, the film has gained quite a cult following since then, thanks primarily to Disney keeping it readily available via home video (instead of keeping the film on "special release" status, like most of its other animated features). A "restored" version of the film has yet to be released.