Leo Valdez is the great grandchild of Sammy Valdez. He grew up with a physcotic babysitter who was testing him. (All along she was really the goddess Juno in disguise.) By tests, the goddess/babysitter put him in the fire place and watched him. Strangely, Leo did not burn up, which he later learned meant he was a Fire User. The goddess went by a fake name 'Tia Calida' and went through many trials with him. She claimed that she did it because she knew that Leo would one day be her hero and saviour.
One day, when Leo and his mother Esperanza Valdez, were heading out from her workshop, his mother realized she forgot something. She went back to get them and Leo was left waiting. A few seconds later he heard the door shut and he ran back to get her and realized that it was locked. He tried to open it but it was locked tight. That's when Gaea appeared to him, in human form. She wasn't fully awake, her eyes were closed, but she provoked Leo just right so that he used his Fire User abilities and set the shop on fire. His mother was still locked inside the shop and couldn't get out. He ran to the door and pounded on it, trying to get a signal from her. He even tried morse code, but he never got a reply. The building burned around him and when the fire fighters and police came, his mother was gone. They didn't know how he'd survived but instantly the people turned on him calling him a murderer. He turned to his aunt, but she didn't want anything to do with him. He was sent to Foster Care but he kept running away, until eventually he landed in the Wilderness Survival School where he met Piper McLean and Jason Grace.
Leo Valdez isn't the most handsome guy, but what counts is his personality inside. He has curly short brown hair and isn't at all organized in how he dresses. He almost always wears his magical tool belt at his waist and has a mischevious grin. He also has a Mexican appearance.
Leo has a crazy but kind sense of humor. Sometimes, his jokes are hurtful but he doesn't mean it that way. He get's defensive over sore spots but is all very loyal and trustworthy towards his friends. He feels like he's the seventh wheel in the group, because everyone else has a couple and everyone has friends and he's left out. His sarcasm is hilarious and everything about him is comical and funny. He can be serious when he wants to, especially when people threaten things he loves.
Leo is in every Heroes of Olympus book so far. That includes:
- The Lost Hero (main character)
- The Son of Neptune (brief scene near the end)
- The Mark of Athena (main character)
- The House of Hades (main character)
Leo has only one known power and two known 'weapons.'
- Pyrokinesis: This gift is only granted by Hephaestus/Vulcan to whom he thinks is his most worthy child. They tend to be 'dangerous' and 'mess things up' but Leo uses the gift with extreme care. This gift allows him to ignite fire upon his skin and not be burned.
- Magic Toolbelt: His magical toolbelt grants him anything Leo wants as long as it can be found in a workshop. He can also slip something no matter how big into the pockets and it doesn't weigh him down at all.
- Festus: Festus was Leo's bronze dragon he fixed in The Lost Hero. The dragon sadly crashed and was torn apart near the end of the book, and is now the masthead of the Argo II.