Yveltal

Yveltal, also known as Lady Death, is a member of Kalos' Vitality Trio alongside Xerneas and Zygarde, and within said trio is the embodiment/deity of death, destruction, and change, and aligned with Hearts Of Gold. In addition to her usual form of a massive red bird of prey she can disguise herself as other creatures; her most common disguise is a human known as Yvonne, but she's also taken the form of more innocuous birdmons such as Starly.