Fiendish Visage

A ritual performed upon conception imbued the resulting child with a demonic spirit residing in it's body. You have fought most of your life making your actions your own will and not of the spirit inside. Sometimes, in a heightened emotional state such as anger or frustration, the fiend is able to force it's will upon your body and partially transform your appearance as well as your state of mind. Your fangs and horns grow larger, your skin starts to change to a redder hue, and you have an uncontrollably strong and violent temperament. Due to these changes, for the duration of your emotional state, you have advantage on Intimidation checks.