Okay so my fiancee wants to try out pathfinder with me and she is pretty dead set on being a elven ninja...She wants me to help her with a backstory though since I am the DM. I will be running a campaign based in Golarion, a sort of mash up of the two APs Rise of the Runelords and Shattered Star. Any ideas as to how such a strange race/class would go together? P.S. she wants to start as being from Sandpoint and being close with Ameiko.
Well, it depends--how epic do you want the backstory to be, in terms of the campaign?
Elves live for a long time--it takes over a century for them just to reach maturity. So, perhaps, a small family of elves emigrated alongside the Kaijitsus when they came from Tian Xia to Varisia. Maybe this young elf among them was touched, ever so momentarily and ever so little, by the magics of the Kaijitsu Seal, or even just the general magic of the land or of the Kami there.
It's quite possible that this young elf, and her family, has been associated with the Kaijitsus for a long time. Being that she was so young, the character may not really remember Tian Xia or the trip from that faraway land to this one, the one she calls home, but the culture lives on in her family.
Maybe these elves are secret, specially-trained bodyguards for the Kaijitsus. Though she herself was never explicitly told as much, this elf was groomed from her youth to be a ninja in service to Ameiko--taught to harness her racial gifts to deadly effect, taught stealth and subterfuge and just where to strike a foe for maximum effect, the better to end a threat to your master quickly.
This ties her in pretty well with Ameiko, the other Kaijitsus even, as she was probably a friend of her family all her life--maybe her parents died or moved on at some point, and the Kaijitsu clan is the only family this elf has left. It also gives her a good spot in Sandpoint.
By the way, I just realized you said Shattered Star, and I read Jade Regent, so a lot of this information is based on some background info from that AP.
That's perfect though thank you so much! I feel that all the APs are just so much better to me done in a flowing stream instead of separate bodies so adding in a little of Jade Regent is perfect. I'll have to look at that AP so far I have only really looked into RotRL and SS. Even if I don't buy the whole AP would getting the first one of it be worth helping me flesh her character out more for her. She has never played a tabletop RPG before so I wanted her first character to be memorable.
