Milkyway is the 'little sister' of  Andromeda and Prometheus, she often overshadowed by them both in both action and appearance.  She lacks the starry aura and has a blank black tail showing her age of still being quite a young celestial being, in the progress of gaining and unlocking more of her cosmic powers.  Milkyway is still strong willed and spirited, unlike her siblings who crash landed on earth without knowledge of who they were before in space, Milkyway retained all her memories and sought out her siblings to convince them of who they were.   She has been captured and experimented on by humans multiple times and always finds away to escape, along the way she met earth born lab animals and gained great compassion for them.  During one of her captures she was placed in a state of black goo stuck inside a petri dish for many years.  She has been isolated in a sleeping state for a long time and thus is less powerful then her siblings. She was awakened when Nightlight knocked over the dish, once awake she longed to find Andromeda and Prometheus again to try to return them to the stars.