The Black Cauldron game for the Apple II GS was first video game based on Prydain. It was developed at Sierra On-Line based on the 1985 Disney movie, and was released in 1986. The game was notable at the time for having introduced some unique features, including alternate endings dependent upon how you proceed through the game. The game was designed by Elaine Boulay, Nancy Casolaro, Melissa Haldeman, Al Lowe and Roberta Williams, with graphics by Mark Crowe, at Sierra On-Line in 1985. It was made shortly after the first King's Quest game, so it resembled that adventure in many ways. Along with The Dark Crystal it remains one of only a few adventure games by Sierra to be based on films.

The player character is young Assistant Pig-Keeper Taran, who as in the film undertakes a quest to stop the evil Horned King, who sought Hen Wen, the magical pig belonging to Dallben, for her visionary abilities. With these abilities, the King would be able to discover the Black Cauldron and rule the land. Taran's first mission is to lead her to the Fair Folk while the King's gwythaints are looking for them. Should the pig be captured (the game allows either possibility), Taran can go to the King's spooky castle and rescue her. Once inside, Taran will meet and rescue Eilonwy with her magic bauble and Fflewddur Fflam, as well as discover a magic sword. The Cauldron is in the possession of three witches of Morva who will trade it for the Sword. Unfortunately a dragon grasps the cauldron and Taran goes back to encounter the evil man himself. The game actually featured plot branches and multiple endings depending on many variables, such as whether Hen Wen the pig was saved, how the cauldron was destroyed, and what reward was chosen afterwards. This use of multiple endings predated the more famous use in Lucasfilm's game Maniac Mansion by a year.

In order to make the game more accessible to children, Sierra used an innovative idea that would not reappear in the genre for the next 10 years: the text parser was removed in favor of the function keys that performed various actions: F3 would choose an inventory item, F4 would use it, F6 would perform "Use" near the character's location, and F8 would "look". The simplification of the two actions "Look" and "Use" was not reused in Sierra's later games. However, it somewhat resembles the control system of other later simpler point-and-click adventure games, such as the King's Quest VII or The Dig whose interfaces only consisted of "Look" and "Use". Being based on a Disney film, the graphics present some relative "flexibility", compared to the monolithic and straight sceneries of previous and later games.[23]

In recent years, several youtube users have posted videos recording their gameplay. User oldclassicgame had this to say about his video playing Sierra On-Line's The Black Cauldron game:

An graphical adventure game based on the Walt Disney film of the same name where you play Taran, an assistant pig-keeper in the land of Caer Dalben who helps take care of a pig name Hen Wen having magical powers and protect it from Evil Horned King who wants to use the pig to locate the cauldron so he can take over the world. If Hen Wen is kidnapped, you are on a mission to rescue the pig and defeat the Evil Horned King before he locates the cauldron.

Note: Due to too much time spent playing this game, I did not have the chance to include all of the paths mainly due to long lengthy loading times and character moves so slow. However, I did manage to include all endings.
The first set of endings begins at 1:19:23
The final set of endings begins at 2:39:10

Played on Atari ST emulator: SainT emulator with built-in AVI Output.
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