Also I settled in the dungeon. It's where the Slytherin common room used to be. It is now my apartment. Perhaps you can share where you are so we can find each other without having to ask the ghosts.
Finally, the Red Baron said that whatever killed everyone was not the product of Slytherins or even Dark Wizards, but apparently half-blood and Muggleborns doing some and I quote 'indecent Muggle experiments on Magical beings'. I'm not sure what that means, but it's worth investigating (unless someone could get a better answer).