Vardis

Perseus Jackson is a half blood, a demigod and no one that knows him can deny that, everyone just assumes half blood means half god and half human but in Percy's case it is quite different, yes he was half god but he was also half Vampire.

His mother, Sally Jackson was actually vampire royalty before her family rejected her and cast her out for believing that they should live in the human realm.

She was supposed to learn her lesson and come crawling back but once she made a life for herself in the human realm she rejected the idea of going back home.

She met the lord of the sea who failed to realize that she wasn't human and eventually they had a child together, having to abandon her life to marry a lowlife that stank worse than a demigod wasn't an endearing experience for her but she managed.

Perseus was eventually made to go to camp half blood while Sally was forced back to her home to face punishment for breaking the rules of her banishment and consummating with a being from the human realm and worse having a half vampire offspring.

Left alone at camp Percy had to figure out what was going on with his body, random mythological facts appearing in his head and his sudden need for blood plus he had to deal with the lingering feeling of waiting for someone.