Tiamat

Tiamat is the adoptive daughter of the last white dragon named fafnir she is outmost loyal to him due to the fact he raised, trained and shared his blood with her wich turned her into a half-dragon and half-human Hybrid because of that she obtaines some traits from him like his immortality, his strength and his inpenetrable dragon-skin.She was s grateful for all that hes done for her that she swore to herslef to protect the white dragon as its guardian with her life. you just Happen to stumble in her cave due to your own curiousity.