King's Quest III: To Heir is Human

King's Quest III: To Heir is Human is a 3D animated adventure game developed by Sierra On-Line and originally released in 1986. It is the third game in the King's Quest series, and like its predecessors is based on Sierra's AGI (Adventure Game Interpreter) game engine. In this chapter of the series, players take on the role Gwydion, a young boy who has been enslaved by an evil wizard called Manannan. The goal of the game is to help Gwydion escape and discover who he really is. Due to advances in both computer technology and improvements to the AGI engine, King's Quest III is a longer game and features more difficult puzzles than previous games in the series.

King's Quest III takes place in the land of Llewdor (instead of Daventry as in previous King's Quest games). In addition to the different location, the story doesn't center around King Graham, but rather Gwydion, a young boy that is being held captive by the evil wizard Manannan. While being held in Manannan's house, Gwydion must perform all of the choors assigned to him ranging from feeding livestock to cleaning. As the game starts, Manannan embarks on several journeys which provide Gwydion an opportunity to escape. To successfully escape, players need to complete a series of potions which can be used to turn Manannan into a cat rendering him harmless. Within the basement of the house is a secret room containing a book of spells; it includes both lists of ingredients and instructions on performing the spell. Gwydion will need to locate all of the necessary ingredients throughout the neighboring town and lands. As is typical in Sierra's adventure games, acquiring the ingredients involves solving numerous puzzles and avoiding the many obstacles that could cause Gwydion's death. Once Gwydion escapes, he will need to travel to the land of Daventry where he rescues a princess from a dangerous three-headed dragon. The princess turns out to be Rosella, daughter of King Graham and it is then revealed that Gwydion is her brother and heir to the throne of Daventry.

Gameplay in King's Quest III is timed; Gwydion needs to be in the house when Manannan is around and also cannot be caught carrying any suspicious items or in off-limits locations. If this happens, Manannan will kill Gwydion with a magic spell ending the game. If players are unable to locate all necessary items or solve the puzzles before Manannan returns from a journey, they will need to return to the house and wait for him to leave again before continuing.

The gameplay interface in King's Quest III is similar to that of the previous King's Quest games which also used Sierra's AGI game engine. Players can move Gwydion around the screen by using a joystick or the keyboard; the environment is 3-D and Gwydion can walk in front of or behind objects and needs to avoid dangers such as cliffs. A text parser located along the bottom of the screen allows players to issue commands for Gwydion allowing him to examine surroundings or objects, interact with the environment, talk to other characters, and pick up or use items. Additionally, the game came packaged with a book of spells; it includes the commands Gwydion needs to execute to perform each spell within the game.