uboa

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Infamous character from the cult game Yume Nikki. If you turn off the light in Poniko's Room, there is a very small possibility that Poniko will be replaced with Uboa, and simultaneously trapping the player within the room.
A continuous filtered "aaaaaaah" sound plays with its appearance.

Should you interact with Uboa, you will be teleported to a hellish, looping world, where the only way to escape is either using the Medamaude "effect" to return to the Nexus, or to pinch yourself awake.