Sometime during Koridai's history, Ganon and his minions invaded the island. They would then set up bases of operation by establishing "faces of evil" which were areas of the island that bared the face of each minion. A Koridai native wizard named Gwonam, quickly flew to Hyrule to inform King Harkinian about Ganon's siege of the island. Although the King immediately offered his aid, Gwonam explains that according to a prophecy, "only Link can defeat Ganon". Link is then transported to Koridai by Gwonam.
During Link's quest in the island, Gwonam reveals to him that Princess Zelda was kidnapped by Ganon and he has imprisoned her in his lair. Eventually, Link proceeds through Koridai, defeating Ganon's minions and retrieving an artifact known as The Book of Koridai, which is revealed to be enough to defeat Ganon. Link confronts Ganon, who attempts to recruit him with the promise of great power. Link defeats Ganon and imprisons him in the Book of Koridai before awakening the sleeping Zelda. Gwonam appears and congratulates Link on imprisoning Ganon. He shows the two a rapidly recovering Koridai and declares Link the island's hero. Although Zelda still refuses to kiss him as a reward, Link celebrates his success.
Koridai is a densely mountainous island. It features multiple mountain peaks that climb high above the territory and surrounding ocean. The mountainous landscape gives the island a hostile environment, which includes canyons, wastelands, active volcanoes, and waterfalls torrenting down the mountain sides, most prominently in Spearfish Falls. It also has a frozen tundra in the northwest where Nortinka and Serigon Caves are found. During Ganon's siege of Koridai, several of the island's regions were conquered by his henchmen: Goronu, Harlequin, Militron, Glutko, and Lupay. These regions were turned into the Face of Evil, mountain peaks and structures with angry glares in the likenesses of Ganon's minions, which now serve as their bases. Koridians were then enslaved in these areas and transformed into monsters. Ganon also has his own Face of Evil, Ganon's Lair, which sits in the center of Koridai.
The island appears to not have any towns or villages. This is ether because of Ganon's recent siege or the islands' difficult landscape. However, there are some small settlements located across the island. These include a small fishing village along the coast of Crater Cove and a couple of fortresses, most notably Fortress Centrum. However these became inhabited by Ganon's forces following their take over. The island's only known store, Morshu's shop, is located in the Goronu region of the island.
The governance of Koridai is mostly unknown as no authoritative figures are ever encountered during Link's quest. It is possible that the island's Fortress Centrum was a base of military operation before it was eventually abandoned and captured during Ganon's siege. It could also be likely that Koridai is under control of another land such as Hyrule.
Similar to Hyrule and other lands, Koridai's main currency is the jewel-like Rupee, referred to instead as "Rubies". Unlike other lands however, the value of Rubies vary slightly differently in Koridai as their colors are swapped much similar to Gamelon; red is worth one, green is worth five, and blue is worth ten. Rubies are accepted at Morshu's shop in Goronu, but are also notably used to power many of the items and power ups that are founded on the island.
Koridai is populated predominately by Hylian-like humans, who share the characteristic of having pointed ears. Unlike Gamelon, most of the island's population lives in caves, igloos, and hut's. During Link's quest, many Kordians have been captured and enslaved by Ganon's minions or have fled the areas, leaving many homes and settlements of the island deserted. However, a few Kordianis managed to avoid capture and now live in solitude such as Droolik who is all that remains in the Glutko area. Fairies are also known to inhabit the island in the region of Spearfish Falls.
- "Your Majesty, Ganon and his minions have seized the island of Koridai!" — Gwonam (The Faces of Evil)
- "These are the Faces of Evil. You must conquer each." — Gwonam (The Faces of Evil)
- "Koridai has fallen to Ganon and his evil friends! The gentle islanders are being transformed into blood-thirsty warriors." (The Faces of Evil manual, pg. 2)