Nyssa Barrera

Nyssa is a daughter of Hephaestus. She shows Leo around the forge and explains to him about Festus, the dragon they lost. Leo mentions how he wanted a sister that could kick his butt. She then says with Jake Mason injured she is in charge of Cabin 9. She explains to Leo how dangerous children of Vulcan/Hephaestus that can use fire can be.

Appearance
Leo describes her saying she looked like "one of those female action heroes, except for that smiley face band-aid of her chin". In The Lost Hero, she is described as wearing a tank top and a bandanna to tie back her blond hair.

The Lost Hero
Nyssa was first seen when Leo arrived at the forge in Camp Half-Blood and explains to him about the curse that's been plaguing their cabin. She was later seen when Leo comes back from his quest and was one of the people to cheer Leo becoming the senior counselor of the cabin.