Poe is the consciousness of Planet Limbo. She makes her first and only appearance in Season 2, Episode 8.
She is the only living being left on Limbo after a massive armed conflict destroyed all of its inhabitants. Their souls imparted the planet with a "magnetism" that draws in the souls of the deceased, turning Limbo into a kind of purgatory.
Poe is one of the few characters in the series aware of Dandy's identity as a trans-dimensional being. The brief cutscene of her receiving a tuxedo-clad Dandy at the end of the episode suggests that she retains memories of their first encounter, and that she too is kind of trans-dimensional being.
It may be that every time Dandy dies to be reincarnated in another universe, he pays a visit to Planet Limbo and meets Poe.