The Hall of Radiance is the name applied to the largest room of the Iceberg Cavern, which is located in Endless Ocean: Blue World's Weddell Sea. It is a room notable for its spires of ice, as well as the multitude of crystalline formations that cling to the walls. There is a section of this room that is above-water, but nothing particularly of note can be seen if the player surfaces. The only way in and out of this room is the tunnel in the floor of the Hall.
The creatures that live inside of the Hall include shoals of Antarctic Silverfish and a small group of Leopard Seals, as well as the occasional Bald Notothen (which are found only under zoom-mode patches). After the player has gone through the events in the main story that occur here
During the main storyline, the player will also encounter a Spectacled Porpoise (a species that is not otherwise found inside of the Hall) with a white patch on its fin that has been separated from its pod. Its cries of distress sounded so eerie and ethereal echoing through the caves that the player and their troupe believed that it might have been the Song of Dragons.
However, upon discovering the Porpoise and discovering that it is the true source of the mysterious cries, the player will be tasked to heal the distressed creature with the Pulsar, and it will subsequently become one of the player's diving partners in thanks. It is unknown how this particular porpoise managed to find its way into the Hall, considering that the only egress was blocked by ice formations, but it is a possibility that the ice formed after the disoriented creature somehow stumbled in.
Location and GeographyIn order to gain access to the Hall of Radiance, the player must first enter Lower Ice Cave 3 from the main area of the Weddell Sea. After doing so, they will pass through the Crystal Globe, an area named for its beautiful ice structures resembling gemstones, and then go through a twisting tunnel, emerging in the Hall. The first time the player has to pass through the Crystal Globe, the way into the Hall will be blocked by large spikes of ice, which the player must break with the help of the Leopard Seal that lives in the dome. The sound of the Sea Whistle causes the seal to charge at the player, and when the player dodges, the enraged Seal rams into the ice blocking the way instead, breaking it. After this occurs, the Leopard Seal shakes off the impact like it was nothing and continues its rounds of the Globe without engaging the player further.
Four of the one hundred Constellation Coins can be found in the Hall of Radiance, or near it. These include the Cancer Coin, under a zoom mode spot close to the waterline; the Perseus Coin, close to the tunnel that leads out of the Hall; the Uranus Coin, under a zoom-mode spot on the floor of the Hall; and the Crux Coin, not found within the Hall itself but in the tunnel connecting it to the Crystal Globe.