The Dead Zone first comes in the Garlic Jr. saga(from what i've seen). The dead zone is just a black hole. Only garlic Jr. and Garlic can open and close the dead zone. When garlic jr. first appears he tries to trap the z warriors in the dead zone for only 10 years. Gohan gets mad and throws garlic jr. into the dead zone. 10 years later garlic jr. comes back and again, gohan throws Garlic Jr. into The Dead Zone when he opens it. But this time Garlic Jr. set the time for the dead zone forever. Really the dead zone is just a place where nothing happens. You just live in torture of doing nothing and being tossed around by wind for 10 years or forever...