"The Black Cauldron" film was based primarily on the first two Prydain novels with elements from the others. It was the last Disney film produced before corporate reorganization created Walt Disney Feature Animation (later Walt Disney Animation Studios) as a separate division within the company, and the first to be rated "PG" rather than "G" in the United States by the MPAA. Disney's adaptation of "The Black Cauldron" was considered a commercial failure because its gross receipts did not match production cost.