SECOND SEA / SECRET GUIDE

TWO KEYS. DON’T CHASE THE WRONG DOOR.

Ice Castle hides more than a boss fight. The key name matters.

WIKI FIELD NOTES · Reviewed 2026-09-12Read source ↗

THE KING’S FIELD NOTESIce CastleILLUSTRATED GUIDE · SECOND SEA

SEA 2⌖ Ice Castle◇ Explorer

THE PATH LESS TRAVELED.

The Hidden Key and Library Key serve different purposes. Keep that distinction clear before planning your run.

Reach Ice Castle.Locate the castle in the Second Sea.
Read the item name.Hidden Key and Library Key are separate drops, not interchangeable keys.
Follow the matching route.The Hidden Key leads to Rengoku; the Library Key opens access to Phoeyu and the Death Step path.
Use it before leaving.The source warns that both keys disappear when you leave the game. Check the complete requirements in the linked guide.

THE KING’S FIELD NOTESIce CastleILLUSTRATED GUIDE · SECOND SEA

LOCATION REFERENCE / ICE CASTLE

Source: Ice CastleOriginal summary reviewed 2026-09-12. Check the wiki for changes after game updates.