Like the name suggests, the ruins are believed to be comprised of light in a solid form. The interior of the ruins contains many advanced, technological machines. The ruins can be entered three different ways: the main entrance in the front, a secret entrance located on the left from the main entrance, and through an underwater passage from the Great Hollow.
Although the ruins' purpose is unknown, they appear to possess some connection to the Bridge of the Legacy, as it is from here that Vaclav Bolud forces Shirley Fennes and Stella Telmes to raise the ship, lowering the water level in Raging Bay and an adjacent cove to reveal the Bridge itself. The ruins are so-called as they are formed of a material that resembles light itself compressed into matter, although the nature of this substance, which was presumably created by the ancestors of the Ferines, is never further explained. It may be surmised that the ruins are a part of the infrastructure controlling the Legacy, though what role they would have had in ancient times, if any, is never explained.
After Senel Coolidge and his companions fail to save Shirley Fennes in the Waterways, they travel to the Ruins of Frozen of Light in order to make another attempt. Vaclav takes Shirley to the ruins in hopes that he can raise the Bridge of the Legacy. The group sneaks into the ruins after traveling through with a submarine from the Great Hollow. While in the ruins, Vaclav sends a "Megant" to attack the group, but they manage to defeat it. After the group defeats the monster, they arrive in the control room and find Shirley trapped in a container. Senel looks closer into the containment area and also finds Shirley's older sister, Stella, in the machine with her. While attempting to free the two, Vaclav arrives and fights the group, but they are defeated by Vaclav quickly. After losing to Vaclav, he reveals to them that Shirley is not Senel's real sister, and that the only relative the Merines has is her older sister Stella. As Vaclav is about to kill Senel, a golden Teriques surrounds Senel and opens an escape hatch. The group follows Senel down the hatch and lands in the Forest of No Return.
The group returns to the Ruins of Frozen Light during Jay's Character Quest after Jay informs the group that the ruins are a hideout for Solon's ninjas. Jay leads them into a control room in the ruins and tells Shirley to come read a command in Relares. Jay releases a switch and traps the group in a cage of electricity. He then knocks Shirley unconscious and takes her with him. After the group escapes from the cage, a "Dullahan" appears and attacks them. After defeating the monster, they leave the ruins and head to the Oresoren Village in hopes of finding Jay.