"Everything will work out if we work together!"

Human form

Cat form

"Sealed inside an artifact, this entity was rumored to be a dangerous being capable of devouring unfortunate lives that come near it. However, when a wanderer breaks her out, instead of a life-threatening monster, a voice cheerfully greets her, asking to help save Stardust Isle. Despite allegedly able to share abilities, Cosmos was shocked to find she fails to do many things that entities of the same kind can do. However, the rumors regarding her powers aren't completely wrong."

Facts about her:

She's supposed to be a magical creature called cometling, for why she has a human form, that would require a lot of explaining...
She cares about her appearance quite much, and makes a lot of effort trying to look cool
She likes flying to somewhere high up and watch the view, particularly during dawn
Though she has strong magic within her, she does not know how to use it, so she trains magic with Lavender often
She's bad at lying, nor she enjoys doing it
She often suffers from nightmares, so she often finds Lavender for comfort