The black spheres known as Gantz, are objects with seemingly impossible abilities, mass produced in a factory in Germany, using alien military technology. This technology was sent to Earth by a species to help them fight off another alien species that had previously tried to invade them. Each Gantz sphere has a person inside, which the Room of Truth reveals was just a random person duplicated about to provide an interface. The alien broadcast only contained military technology, the point system and other aspects created by humans.
Facts that are known about Gantz
- Gantz is able to remove every part of someone who recently died, down to the last drop of blood, and then generate a perfectly healthy copy of them in the Gantz room or elsewhere, as shown in the revival of Tae Kojima.
- Gantz can restore anyone who died, to the point at which last he had scanned them in, that is before sending them on a mission, etc.
- Gantz is able to erase someone's memories, doing so when he sends them out of the game, although sometimes a few still linger.
- Gantz is able to send people to destinations around the world, and bring them back again.
- Both the Gantz sphere and the individual inside of it cannot be killed from players in the game at least. This is shown on a couple of occasions where he is shot by the X-Gun as well as stabbed by Hikawa, to no effect.
- The naked man inside the sphere is able to come out. We don't know yet if this happens on every single mission or is a consequence of the Katastrophe time-counter.
- After Katastrophe, other people have been seen to use the controls inside the Gantz spheres, to access at least some of its abilities. So far they have done this to bring over people that were still alive, and send them to the alien world/dimension and back again. They were not seen as able to bring forth hordes of advanced weaponry and equipment for them though.
- Gantz is able to give people superior equipment, but only once they prove themselves with a high enough score to get the Hundred point menu. Whether all of them follow the same rules, or if they are able to try different things, is unknown.