The Sealed Door is a recurring item in Chrono Trigger and is a technology of Zeal. Created in the Antiquity era, these doors bar access to powerful items. The only way to open them is through use of a Dreamstone Pendant. They are primarily found in the Future era, and while most of them lock off treasure (the doors in the Bangor, Trann, and Arris domes), the one in the Keeper's Dome is imperative to the story, as beyond it lies the Wings of Time (albeit without its wings).