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Nightmare Fuel: Magic Knight Rayearth
The monster of episode 8. It's Hikari, the cute fox Hikaru befriended. It reveals itself by bursting out of its skin, and its mouth is suddenly full of razor-sharp teeth.
Cephiro slowly decaying as the series goes on. At first the world is always in daylight and has beautiful scenery, but as time progresses earthquakes are more frequent, storms spring up, and it turns into Always Night.
The end of the first part has Princess Emeraude's descent into madness and the awakening of her Superpowered Evil Side.