The Child of No God(Percy Jackson)

Lily Martin managed to gain access to Camp Half Blood but when nobody claims her for three days the campers start to grow suspicious. Just when the head of the Ares cabin speaks up, her Grandfather appears to reveal all. Lily's mother was a war here who fled to the mountains with her father but when Lily's mother, Roxie, gave birth they decided three demigods would attracted too much attention to monsters. Lily grew up in a Foster home but now she knows her parentage, she's sent on a quest to save a captured god, while trying to find out if her mother survived monster attack that made the mortal news.

(Credit to Rick Riordan for the idea of Camp Half Blood, some other story plot, and other characters.)