|“||Come on joker boy. I'll show you around.||”|
Nyssa was born to the god Hephaestus and an unnamed mortal. When the daughter of Hephaestus was old enough she was brought to Camp Half-Blood by a satyr and was claimed by her father.
Nyssa is temporary head counselor while Jake Mason is recovering from his injuries. When Leo Valdez arrives at the forge in Camp Half-Blood, she explains to him about the curse that's been plaguing their cabin since the past head counselor Beckendorf died and how they lost the dragon. She is later seen when Leo comes back from his quest and is one of the people to congratulate Leo on becoming the senior counselor of the cabin.
Nyssa and Harley did not participate in the three-legged race, for they were in charge of it. When Leo returns to Camp Half-blood six months after the Siege of Camp Half-Blood, all the campers take turns "greeting" him. Nyssa slaps Leo and berates her half-brother in rapid Spanish.
Leo describes her saying she looked like "one of those female action heroes, except for that smiley face band-aid on her chin." She is described as wearing a tank top and a red bandana to tie back her dark hair. She is also mentioned as having coco-brown skin.
Nyssa is a strong willed young woman who cares for her half-siblings and is willing to step up if she is needed in a leadership role.
As a child of Hephaestus, she has the following abilities:
- Technokinesis: As a daughter of Hephaestus, she can manipulate machines.
- She is an expert mechanic.
- She can sense machines, mechanics, or metal.
- She can identify machinery type and use by touch.
- She can sense faults in a metal ore.
- She can find and sense traps in the ground.
- She is an expert builder.
- Nyssa is a name with various meanings around the world, such as “beginning” in Greek and “sign” in Hebrew.
- Barrera is a name of Spanish, Portuguese, and Italian origin meaning “barrier”.
- Nyssa is the only daughter of Hephaestus to appear in the series as Heloise, a daughter of Hephaestus who attended Camp Half-Blood in the 1940s, was only mentioned via her notes and seen in a picture.