Please please please use proper capitalization and grammar. Sorry if that sounds patronizing.
As for your backstory. There's the Worldwound, a terrifying locus of demonic intrusion, corruption and activity. There's Ustalav, pseudo-transylvania, land of a thousand mysterious mystery horrors. There's Cheliax, land of demon binders and experimenters. And there's the Mana Wastes, the no-mans land left over from a massive war between two archmages and their countries, land of warped and strange creatures. One of 'em should do ya.
GM Arkwight gave excellent advice. There's also the darklands (aka the underdark from D&D), which is mostly unknown to the surface populations. You could literally pop up from there anywhere in the world; just need a cave that goes deep enough.
You could leave your backstory blank, and say you've lived in Kaer Maga. It's a great place to be if you're strange, monstrous-looking and an outsider. And it is in the region of Varisia where Rise takes place.
Perhaps you're from one of the other continents of Golarion, and choose to remain a mystery. Perhaps from Casmaron and you lived in the Windswept Wastes, too close to the Pit of Gormuz. Perhaps you're from the destroyed continent of Azlant and its various islands, mutated after it's destruction to survive the fall of the Runelords millennia ago. Or from the island continent of Sarusan, almost completely isolated from the rest of the world's species. The Darklands is also a very good option. There's plenty of choices, if you're creative enough. There's also the other planets in the system that have their own races and cultures.