We can’t make a Sierra games retrospective without beginning with the first graphic adventure ever made for the IBM PC and Sierra’s first big hit: King’s Quest: Quest for the Crown.
As I mentioned in my Sierra historical retrospective, IBM needed a game to promote their new computer, the PCjr, and approached Sierra to finance it. Sierra took full advantage of the proposal to develop a game engine called Adventure Game Interpreter (AGI) and with it, Roberta Williams developed a game based on an On-line Systems (Sierra’s former name) title: Wizard and the Princess (AKA Adventure in Serenia). Like that one, she wanted to make a game based on fairy tales and fantasy: of a gallant knight in a quest to save a kingdom.