Shadowgate is a 1987 "point-and-click" adventure video game originally for the Mac and is the most popular in the MacVenture series. It was also released in 1989 for the Nintendo Entertainment System, where it garnered mild success. The game is named for its setting, Castle Shadowgate, residence of the evil Warlock Lord. The player, as the "last of a great line of hero-kings" is charged with the task of saving the world by defeating the Warlock Lord, who is attempting to summon up the demon Behemoth out of Hell.
Source: Wikipedia, "Shadowgate", available under the CC-BY-SA License.