The Sign of Chaos is a sequel to Descendants of Danaan, set in the same fantasy world based on Irish mythology. The legendary hero has accomplished his mission, but the forces of darkness were too strong, and as a result four kingdoms were engulfed in chaos, overrun by monstrous creatures. The hero travels to the land of Fianapia and teams up with the local princess to cleanse the country of evil. The basic gameplay system is similar to that of the predecessor, relying on Ultima-like role-playing template with free-form exploration of a vast overhead map. Dungeons are viewed from a top-down perspective as well. Turn-based combat takes place against randomly appearing enemies on separate battle screens where tactical navigation is possible. Changes include graphical towns, character icons displayed during navigation, and the possibility to converse with or even recruit certain type of potentially hostile creatures encountered in the wilderness.