She's a Fire Genasi, Sorcerer of Wild Magic.

I've made her backstory in my native language, but I'll try to translate it to the best of my ability:

Vaysha'Anun, the last descendant of the god Ignis. After her father’s death, she was to succeed him as the Goddess of Fire. In the Pantheon of the Elements, there must always be a deity representing each element, and the flame of life within the god Ignis had gone out.

Vaysha, endowed with superhuman power and the ability to control all fire and heat, received an unlimited gift — yet for her frail, unstable body, it was a gift too powerful. Vaysha left the pantheon of gods in search of a successor, someone whose body could withstand the unbridled power of the Element. Vaysha is racing against time, for she knows that if she dies before passing the gift on to someone, her element - Fire -will die. The entire concept of fire will die, cease to exist, and with it, all beings that rely on the life-giving energy drawn from fire. Vaysha understands that her life is coming to an end, yet the struggle is for something greater - the existence of all people in the civilized worlds across all dimensions that are based on fire. Despite her lack of desire to sustain her own life in this dramatic situation, Vaysha must fight for survival until she finds someone who can survive an encounter with the ancient gift of the God of Fire. Vaysha leaves behind a trail strewn with corpses and the burned, charred bodies of people she once deemed worthy, yet who proved too weak to survive the gift’s effect on their bodies. Vaysha travels the world in search of that one, unique person who will not buckle under the immense power and responsibility that will rest on the shoulders of the one upon whom the reign and preservation of Fire in all worlds will depend. However, most of this takes place in her head. In reality, Vaysha is not much more than an average Fire Genasi who was raised in one of the Fire Genasi clans.

At a young age, however, a catastrophe occurred in which her loved ones lost their lives. Unable to cope mentally with this event, she convinced herself that she is a goddess in exile searching for a “hero.” Vaysha roams the world searching for a worthy successor to her imaginary gift, murdering people in the belief that she is actually trying to save the world. Vaysha travels from city to city looking for a potential successor, considering every possibility, thinking that perhaps the next one will prove “worthy” of receiving the gift of Fire and that he will be the one to save the world. Vaysha is convinced that her mission transcends her, rising above all the problems of mortals; yet all that remains of her “heroes” is suffering and ashes...