Mutilated cadaver

The nations of Hetalia have been invited to a horrid mansion, leaving themselves with two choices in mind. Kill, or be killed. Their is a master who tells them what to do. But it they reject it or do it incorrectly, they will die. Each of them holding a dirty little secret of their own have to be sacrificed to help the others. They need to work together to get out. But who will be the one who tears them apart?