This is where the duration of Spacial Rider shall take place.
Planet Prison is a man-made planet (simular to the Death Star from Star Wars) that has a bright blue electric current swirling around it, like Saturn's rings. Inside the core of the planet is the furnace, which is where the boss battle takes place. Closer to the outside, the prison cells are located. There is a small reward for finding keys to release the convicts, but they can turn on and fight you. Guards constantly patrol the Planet Prison, because of the layer of Guard Rooms around the Furnace.
The entire planet is inhabited by creatures who consume electricity and can survive a powerful electric blast. They also act as guards, and keep the prisoners in check. Their job is to destroy or capture intruders. If they fail, they usually side with the intruder and live until their life bar is depleted.