Title: Snape's Demigod Daughter

Rating: T

Summary: Cassandra Snape comes to Hogwarts during Harry's third year. She's different from other students right from the start. And she has a very nasty view of the word 'Muggle.' To make things even stranger, for Harry, she's Petunia Dursley's sister and brings her sister along for the ride. A crossover of Harry Potter and Percy Jackson.

Disclaimer: I don't own any of Rowling or Riordan's characters and I'm making nothing from this.

Chapter 1

Cassandra Snape was glaring at the train full of witches and wizards as though they were a very bad annoyance. She didn't want to take the train full of bigots and blessed children that would grow up to become bigots. The damn burning times was over, if they hadn't gotten the damn memo. Cassandra was wearing a shirt that was in a nice lavender color, jeans, sneakers, and a leather jacket that had all sorts of magical symbols. Around her neck was a pentacle that was made of real gold and diamonds.

A gift from Lou Ellen!

Gritted her teeth she climbed on board and went looking for a compartment. Every last one of them was full except for one that had only four people. She knocked and a bushy hair girl went to open it.

"Everywhere else is full," she told the girl, "Can I sit here?"

"No," a boy stated and slammed the door in her face.

She knocked on the door again and before it was even opened she forced it open and said one word, "MORON!" And then slammed the door and marched away.

"It's not that bad," the woman that pushed the food cart said.

"Yeah, it is," Cassandra told her. "Wish I had someone to talk to, maybe my other sister."

"You can always write to her," she said. "Well, need to go off and sell some food."

And she left Cassandra alone.

"No, I'm not writing to her," she said, "I'm bringing her here."

Now that was a bright idea.

Unknown to any of these bigots who would never change their ways, Cassandra had one sister that lived in England. Her name was Petunia Evens, though she heard that she had married some mortal and was now Petunia Dursley. She had come to Camp Half-Blood when she had been seven and thought that she was the only witch in the family. When it came out that her sister had been blessed by their mother, she was angry with her. Lily grew up to be just like all these others, a bigot.

Everyone here thought that they had to keep their powers a secret, even had laws against talking about magic. Cassandra had no problem talking about magic in-front of average people and even wore a pentacle with pride. Yes, some people disliked her because she was a witch but no one had tried to kill her. People were a lot more open minded about the magic business then these blessed would like to think. Petunia powers were beyond anything that these blessed could even grasp.

While the blessed relied solely on their blood, children of Hecate relied on their mother. She was the deepest of magic, she was the strand that kept the magic together, and all her children could do beyond exceptional things even before they were six. Also Petunia would give her someone to talk to. She raised her hands and chanted the spell that would bring her sister to her.

A couple of moments later Petunia Dursley, demigod daughter of Hecate, stood there.

"What the? Cassandra, what is going on?" she asked.

"Well mother has me go on this quest and I needed someone to talk to," Cassandra told her.

"You know that my husband is going to notice that I'm gone," she said.

"Can't you make a double?" Cassandra asked.

"Of course, but that's not the point," she said and then, "Okay, but only this once."

Petunia suddenly glowed with blue light and a double of hers appeared. She sent it off with its mission and soon her sister was setting down in one of the seats.

"So what's your mission?" Petunia asked her.

"I'm supposed to protect Harry from Peter Pettigrew and keep him from aiding Tom Riddle."

"The same one that Uncle Hades keeps on ranting about," Petunia said and I nodded. "Gods, I wonder when someone was going to try and help him return to power."

"I don't know why I even have to come," Cassandra told her. "I mean, all they do is talk about how much better they are than other people just because they have magic."

"I know, it's hard," Petunia said, "It was even more horrible to see my own sister buying that load of hogwash. No one is better than everyone else, not even those blessed by mother. Tom Riddle is a second rate wizard, but everyone is scared of him because he appears to have greater powers. He doesn't, we do!"

"I would love to revoke mother's blessings on all of them," Cassandra snarled. "Let them know what it's like to be like the very people they hide their powers from."

"Not so fast," Petunia said. "What year are you going into?"

"Third," Cassandra answered.

"Then show up the most talented third year and that will be good enough revenge," she said. "Spend your entire year proving that you're better than a blessed. I'm sure going to stick around for that."

That sounded like a great idea.

The train continued to move on, both daughters of Hecate practicing their spells. When the train suddenly came to a stop Cassandra knew that they couldn't be there already. Petunia's eyes glowed red and she stood up.

"Hades ghouls," she snarled. "How, in the name of Tartarus, did they get out of the Underworld?"

"I don't think that I want to know," Cassandra commented. "But I have a bad feeling that this has something to do with these damn blessed."

The compartment door opened and in glided one of Hades ghouls. It took one look at us and bolted. Yeah, must have a memory of Petunia kicking his ass or something.

"Come on," Petunia said, "I want to practice with my sword."

The other Dementors were busy checking out compartments but turned when they sensed them. Both demigod's eyes were burning bright red and if the ghouls couldn't be scared of anything the combined powers of two children of Hecate was enough to almost send them scrambling. They must be the retarded bunch because they were slow to back off.

" (Get the Hades out of here)," Cassandra commanded.

" (Before we have ghoul for dinner)," Petunia threatened.

They bolted, causing the lights to come back on.

"Thank the gods that's over," Cassandra said, her sword vanishing back where it came.

"To bad, I wanted to send some ghouls back to the Underworld," Petunia said, her sword vanishing as well.

"Maybe next time," Cassandra said and they headed back to their compartment.

"So does your dad know that you're here?" Petunia asked when they were back in their seats.

"No," she answered. "I don't think that the Headmaster can place me with my father."

"To bad," Petunia said, "I want to see his face when you arrive."

"I've got a funny feeling that he still won't be able to connect me to him," Cassandra told her.

"Well if he can't, I'll hit him in the back of the head with my sword handle," Petunia told her. "That should knock some sense into him."

"Thanks, I'm sure it will," she said, glad that her sister was here.

The train then slowed down an hour later and came to a stop. Cassandra had already changed into the horrible robes that were on her list. She gritted her teeth. Why couldn't they dress like normal people or was that beyond their ability. Petunia had changed into a black chiton and had a small dagger at her waist. The dagger had only one purpose, sacrificing black puppies in the name of Hecate.

Which she did.