Dark Seal

A dark seal (邪結界, じゃけっかい), also known as a "demon's cage" (悪霊の檻, あくりょう の おり), is a type of supernatural phenomenon in Fatal Frame: Shadow Priestess. When a location is placed within a dark seal, it is shrouded in perpetual darkness, and spirits become more visible and aggressive. Anyone who happens to be within the seal will be trapped there until it is removed, unable to leave by normal means. It is also possible to place dark seals within one another, so as to create a labyrinth that must be broken by solving a riddle.

In Chapter 10, the necromancer places a dark seal over Karasawa Elementary, trapping the Modern Architecture Group and the Moebius urban explorers inside. The seal is broken by solving riddles, and also by learning the identity of the Necromancer who created it and purifying them. In the final chapter, when the seal is broken, the whole building collapses, similar to the ending of Fatal Frame.