You are Fiend

As an action, you can change your body type. You determine the specifics of the changes, hair length and style, and sex. It does not change any noticeable features such as horns, tail, skin tones, or bonestructure. You can also adjust your secondary sex characteristics and weight as a different gender or a mix of many though none of your game statistics change. Your clothing and equipment aren’t changed by this trait.

You stay in this form until you use an action to change it. Your true form is whatever you are at the time. 

Thanks to your fiendish heritage, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You have resistance to fire damage

Ability score increase