When Buttercup was young she would aid the spirits of the forest she lives in however she could to keep her fellow forest dwellers comfortable. Eventually the spirits found her to be worthy enough to be able to aid them with something much more important...getting rid of those who meant the forest harm and to get rid of those who "overhunt". The spiritual empowerment and her task at hand changed her fur to black and red as well as her eyes. She tends to be in her normal form whenever she isn't doing her duties, but can change her looks at will...she is however forced to change her look while doing her duties as she is otherwise weaker. Her empowered form tends to be less carring and more violent as this form is meant to attack those that harber ill will, but if she enters this form while not attending her duties she can control her attitude and behavior...there is however a more powerful version of this form but it is only used in the most dire of situations

Art by  krushi.kromsai