A boundary between visible structures and a usable game system.
Fortress structures appear in Interlude, while their gameplay role belongs to later updates. The presence of a fortress on the map does not establish a working capture or reward system in standard Interlude.
A fortress landmark is not evidence that a fortress-siege registration, capture schedule or reward loop is usable in this chronicle. When planning clan activity, use the documented Interlude castle-siege and clan systems. If a server advertises functional fortress sieges, check that server’s own rules before applying its requirements to standard Interlude.