The Light Quest is the quest to get the gift for Light Magic.
To complete this quest, your character must go to Luminous and talk to the man at the entrance to the Luminous Labyrinth. If your character has Shadow Magic, or is Riki or T260G, then the character remains behind as humans and mystics without Shadow Magic enter and exit the Labyrinth. If your character is human or half-mystic and lacks Shadow Magic, you must traverse the labyrinth, using mirrors and switches to guide a beam of light to the end. Only humans and mystics without Shadow Magic can accompany you.