Eris is an alien who fell to this planet by accident. She needs to fix her ship before returning to her home planet.

Regarding her voice, I imagine her sounding high pitched but not exactly like a child. She's an adult after all. She delivers all of her lines either flat or with a curious tone, since she isn't from this planet.

She's oblivious to everything and everyone, she has a very hard time understanding people specially. She takes things too literaly.