The Nexus is the place where Fluorette is taken to outside of the Shrine after entering the Spirit Realm and exiting through the main door. From here, Fluorette may choose from four doors which serve as gateways to four different Spirit Worlds. All Prayers are found from taking the respective paths nessecary starting from the Nexus.
Black door will take you to Clockwork World.
White door will take you toSnowy Streets .
Dark red door will take you to Bleeding World (page needed).
Orange-black door will take you to Playground (page needed).