Twin Star is the group name for the diametrically-opposed planets Sperity and Toruin. Autobot Headmaster Highbrow likened them to heaven and hell - while Sperity is rich in energy, covered in glistening cities and populated by small robots (prosperity, y'see), Toruin is barren and lifeless, with nothing but rocky deserts on its surface (Toruin, you get it?). The two worlds, however, are connected by a massive tunnel-bridge that allows transit between them.