The Crystalization of Mana, Ideals, and Emotions.

Noah is the final boss of Rabi-Ribi's main game.

A bunny-eared girl gathering mana for some mysterious plan. Her body is made of liquid mana, and feels like a thick, sticky slime.

She's very rude to Ribbon throughout the story, as she wasn't "part of the plan".

Due to an unexpected event, her body slowly broke apart and her personality also changed a bit.

-Source: Rabi-Ribi Artbook

Noah was once an inhabitant of Rabi-Rabi island, in the days where bunnies weren't considered rare, or extinct even.

A great tragedy involving the outside world caused her to sacrifice everything she had to keep Rabi Rabi Island safe.

Utilizing all the mana from her fellow bunnies, she managed to protect the island through means currently unknown.

Although, after doing so, her existence was completely erased from everyone's memory. It is likely she put the shield in place around the island, and enlisted Pandora, Rita and Ashuri to maintain it in her absence.

While doing so, she lost her physical body, and was exiled to the outside world.