The Establishment of the Tower
The Establishment of the Tower followed the Peace Treaty of Hope and turned its settlement into a permanent institution. The treaty required a Tower to be built in the Eterna Mountains, where it would guard the Gate, and appointed the demon hero who had helped end the Demon War as its guardian. The resulting institution, the Tower, was designed to prevent the newly ended war from beginning again at the crossing.
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Foundation under the treaty
The establishment of the Tower converted the settlement that ended the Demon War into a permanent border institution. Under the Peace Treaty of Hope, the Eterna Mountains became demon territory on the human side of the Gate. A fortified residence was raised around the crossing, and the demon hero Shun Sato was appointed its guardian.
The office carried three essential duties. The Lord had to protect the Gate, prevent unauthorized passage, and remain neutral in human politics. The first two made him the armed guarantor of the treaty. The third denied him the freedom to use that power in the political disputes of the human kingdoms.
The Lord's confinement
Public history treated the appointment as an honor. Shun experienced it as supervised isolation. His movements beyond the mountains were watched by parties who feared his strength or wanted him executed, and any intervention in a human conflict could be interpreted as proof that the demon guardian favored one crown over another.
The Tower was consequently both home and prison. Shun built a household within it, but its great halls remained deliberately closed to ordinary visitors. Zero controlled the perimeter, planted mana-sensitive threads through the Dark Forest of Eterna, and met travelers before they could approach the mountain. The barriers around the estate and the hidden portal chamber beneath it made the Tower defensible from either realm.
The hidden household
Volume II reveals that the apparent emptiness of the fortress was misleading. Most members of the Household of the Tower could reside within Shun's shadow and appear when called. Zero administered the estate and guarded its approaches; Mimi Sato served as healer and daughter; Suzu repaired damage; Roku defended the portal; and Ryosuke existed as a weapon Shun released only under extreme circumstances.
This concealed strength explains how the Tower could function as a border fortress without a visible garrison. It does not establish that the household participated in every action publicly attributed to Shun.
The Gate beneath the Tower
The interrealm route lies in a vast underground chamber reached through a concealed passage behind the Lord's study. Its emerald portal opens into a cathedral-like portal hall in the Frontier. Passage can be guarded physically by Roku and strategically through the Tower's barriers. Shun also developed long-distance shadow navigation by leaving fragments of his shadow at places of exceptional importance, allowing him to reach selected locations without crossing the intervening distance normally.