Idun Shrine (イドゥンの祠 Iduun no Hokora) is located north of Garden Hill and is accessed through Follower's Path. It is often visited by Ascetic Reithol, who is the Guardian of Idun. He protects the shrine exterior from monsters. Vardarta Dragon, Hunovious, and Raybius are encountered within the shrine.
A silver haired man forces Ascetic Reithol to open the shrine against his will. He then releases an evil spirit that merges with Idun, causing Idun to mutate into a terrible creature. Idun then goes to Garden Hill and spreads scales that produce a harmful odor, then retreats back into the shrine. After neutralizing the scales and the harmful odor, Avin, Rutice, Lucias, and Archem are able to open the entrance of the shrine with the help of Ascetic Reithol. They head into the shrine to free Idun from the evil spirit possessing him. Idun grants Avin the sacred treasure "Delleboura", the Right Arm of Bardus, and the ability to summon his relatives through spirit magic.
There are various passageways which lead into different floors and areas of the shrine, as well as hidden passageways that are not visible to the player. All of the torches and sources of light glow with a green hue. There are several chain handrails found at random spots.
- Even though Ascetic Reithol defends the shrine from monsters, it seems there is an exception for the monsters that actually live within the interior.
- Idun Shrine is the second shrine that Avin visits.