The Forbidden Tower is a sequel to The Sign of Chaos and is the third game in the Tir-nan-óg series of role-playing games based on Irish myths. The plot continues the events of the previous game, as the legendary hero and the princess of Fianapia travel to the land of Serokyu, the fifth kingdom that became affected by the ensuing chaos as the light of the ancient goddess Dana began to fade away. Visually and gameplay-wise the game is almost identical to its immediate predecessor, offering the same Ultima-like mechanics with open-ended exploration and tactical turn-based combat.