Kaocho Palace
Kaocho Palace is a location in Golden Sun: Dark Dawn, located in the town of Kaocho in the Ei-Jei region. The palace is open to the party as soon as Kaocho itself is entered for the first time, but the ability to enter it again becomes permanently locked off the moment the throne room is first entered (which will result in the party being deposited inside the Ouroboros dungeon with the Wo's Letter important item in your inventory). Therefore, an Herb that can be found in one of the two jars in the right warehouse is technically missable content. During this brief window of opportunity to explore the palace, the party can head left and reach the blocked-off "formal entrance" into the Ouroboros dungeon underneath the palace.
Story
Kaocho Palace was initially built by King Wo after the city was founded. For unknown reasons, King Wo chose to build the palace on top on of ancient ruins, the Ouroboros labyrinth. The palace not only served as the personal residence of King Wo, but as his center of government. Thus, his advisers Meisa, Kan-Shuku worked there.
During their travels, Matthew's party of Adepts comes to Kaocho for several reasons. They are not only searching for a way to enter the Ouroboros to obtain the Sol Mask within it, but to find a way into Ayuthay. Ayuthay had been under attack by Kaochan soldiers, who would only accept orders from King Wo.
Matthew's party is allowed into the Palace after the guards learn that the group consists of Adepts. In the throne room, the Adepts hide and overhear a conversation between Wo, his two advisors, and Chalis, who they quickly associate with Blados. Chalis's personal soldiers force the Adepts out of hiding, and informs them of the Sol Mask hidden in the Ourboros. King Wo requests that the group enter the Ouroboros, get the Sol Mask, and bring it to him, as he wishes to wage war with it. However, King Wo's advisers suggest that the group assist in the siege of Ayuthay. This plan is approved of by King Wo, and Meisa writes up a letter granting the Adepts entrance into Ayuthay, which is given to Matthew. The group, particularly Tyrell, is putoff by the request, and refuse. Out of anger, the King orders the Adepts removed. Kan-Shuku then opens a trapdoor below the Adepts, which causes them to fall into the heart of the Ouroboros.
During the Grave Eclipse, the few remaining Kaochan survivors of the monster attacks are brought into the palace with King Wo. The palace is firmly locked and apparently remains safe. However, the ultimate outcome is unknown.