Aeris the Hedgehog is an anthropomorphic hedgehog/Black Arms hybrid.
She was eventually captured following her creation and put into stasis by G.U.N. when she was deemed as a threat to humanity.
Fifty years later, Aeris was released by Dr. Eggman in order to assist him in his plan to conquer the earth.
Aeris lost her memories and as such, sought to uncover the truth of her past, during which she met Black Doom and the Black Arms.
From there, she continued her mission to protect humanity.