Alex is the Norse demigod child of the god Loki (in a female form) and Mr. Fierro, a mortal businessman. Due to Alex‘s gender identity and being the child of a Norse deity, they were constantly berated, harassed, and assaulted by others and eventually disowned by their family. After dying and being chosen to become an einherji their half-sister, Samirah al-Abbas, Alex is now the newest named resident of 
the Hotel Valhalla and a hallmate to Magnus Chase and the other occupants of their section of Floor Nineteen. Alex is currently the significant other of Magnus Chase.
Birth
The Fierro family is influential, which was what first attracted Loki’s attention, causing the trickster to seduce Alex’s father, a married businessman, in the form of a “voluptuous red-head” and tricked him into having an affair with the trickster in his female form.
Nine months later, Loki returned at Alex’s dad’s doorstep and left him with their child. The family didn’t take the news well, especially after Loki permanently lifted the Mist from their eyes.
Early Life
Alex lived in a three story mansion in either Lexington or Salem. White painted columns were at the entrance, and honeysuckle bushes were planted in the front yard. There was also a porch, and an American flag rippled on the porch.
Alex spent their life being resented for both their Norse heritage and their gender fluidity by both mortal parents. He would be bullied, both verbally and physically, by his classmates and berated by his father while his mortal step-mother did nothing to prevent this domestic abuse. Her parents resented her and thought she was embarrassing, and his stepmother was not happy to have him there. They told Alex that Loki put ideas in his head and corrupted him, blaming him for being genderfluid. Her family was rich, but they didn’t care about feelings and only a son and heir. Alex had other siblings, but their relationship was unknown, but her father thought of them as his “real” children. He also thought Alex’s pottery was garbage and said she had so much potential, and wanted him to be normal in his twisted way. As for Loki, she would show up and try to “parent” her.
She was very close to her Abuelo, an immigrant from Mexico, and he taught her pottery. He told her about old Mexican myths and legends, and talked to them about their heritage, saying how her family had been making pottery for centuries, before the Aztecs. His grandfather supported who she was as genderfluid and honored it, telling her about duality people with two faces, two aspects for each gender. Her and his grandfather also discussed ancestors sculptures, because her grandfather wanted to understand it and reclaim his heritage. This infuriated their father, saying that he was putting ideas in her head, and hated that he was finding validation from their family.
Alex hated her father’s pottery business, and called it crap, since it was machine made and not done the old way like her Abuelo. The company was big when Alex was around six, after her father took over and her Abuelo died, when her father made machine made silverware and home goods. Because of this, her father tried to make Alex into a businessman, grooming her to take over the company, discrediting her Abuelo’s ideas, and destroying his art, but Alex didn’t let him. He didn’t understand why Alex didn’t want to make money off of pottery and hated when she listened to her Abuelo’s legends. He made millions and it was a big name, until they realized the quality was going downhill and it became unpopular.