Tir-nan-óg: Descendants of Danaan is a role-playing game based on Irish mythology, more specifically the story of Tír na nÓg (the land of eternal youth) and the Tuatha Dé Danann (people of the goddess Dana). The main plot of the game is only loosely based on actual Irish myths and involves the fictional kingdom of Annafofo, the assault of demons, the abduction of the princess, and a legendary hero who must rectify all that and restore peace in the land.
Despite its Japanese origins, the game follows a Western template, focusing on non-linear exploration rather than a character-driven plot. The game begins with the player controlling a single pre-defined character, though some NPCs will be able to join the party. All navigation in the game is done by moving an arrow representing the party on the world map or through the dungeons, which are viewed from a top-down perspective as well. Towns have no graphics at all and all interaction there is menu-based. Turn-based combat takes place on separate overhead screens and resembles that of Ultima games, allowing free movement on the battle field.