A Gantz sphere is a device that features in the series Gantz.
It was known that the spheres were constructed with a combination of human and alien technology. Their creation was largely unknown though it was shown that factories were responsible for creating the spheres with some being located in Germany where numerous Gantz were constructed in secret operations. At some point, a Gantz sphere was allocated to the area of Tokyo in Japan where it manifested at night in an apartment. This Gantz began its normal operation in selecting hunters that had died in their lives and created duplicates that were tasked with eliminating targets in a set area as well as under a strict time limit. The process saw many of the hunters being killed during their operations and being unable to reveal the existence of the sphere that would terminate anyone that threatened to expose it. Among the people selected was a high school student by the name of Joichiro Nishi who had committed suicide in his life and was duplicated before the sphere. He participated with others during the hunt and proved to be a capable hunter that was actively able to use the equipment provided to him. In time, he managed to learn several of the sphere's secrets and proved to be the only survivor when Kei Kurono appeared in the apartment.
In appearance, Gantz resembled a solid black sphere that was around the size of an adult human being. Its surface was completely smooth but by the front the device projected a series of text in Japanese. These ranged from derogatory comments to a timer and even mission briefings to those it manages to ensnare on its mission. Initially, Gantz remained inactive but when in operation it was would start a radio calisthenics program as preparation for the hunter's mission. This would see it project the target data on the front that included some details on the alien opponent such as their likes and issues that anger them. Once done, the sphere would open two compartments by the side that contained suitcases for equipment and racks for guns. It was at this point that one can see an adult human seemingly serving as the core for the sphere. These people were seemingly in a coma-like state where they were in a curled sitting position and inactive. Numerous wires were hooked onto their body with a breather also being around their mouths. When the sphere was being obstinate, a Gantz hunter was able to coerce it by putting a finger in the human core's ear and twisting it. The occupant of the sphere was also seemingly immune to the weapons provided by itself. Gantz demonstrated a vulgar personality as the text it would project would often give derogatory comments to the various hunters and tell them that they had to obey the sphere. Despite the mission parameters, Gantz would not provide the rules for its hunts which meant that many hunters did not know the fatal consequences of disobeying the sphere or breaking its rules with only survivors of previous hunts aware of these guidelines.
Hunters were selected from around the city where through avatar intermediaries the sphere would find prospective candidates. A common factor in all these hunters is that they were normal humans who died during their life. This could be either through accidents or suicide or other events but during that moment a teleportation beam occurred where the sphere would manifest the dead person in an apartment. In truth, these individuals were not truly saved from their deaths as the teleportation actually created a duplicate before Gantz with the original technically being dead. However, on rare occasions, sometimes the sphere would create a duplicate but the original template would survive their near death experience. As a result, this could lead to two versions of the same person being alive with one being the original and the other the duplicate who had all scars removed from their body. Within the apartment, the candidates were unable to leave or touch the handles giving the appearance as if they were ghosts. Once all the candidates were selected, Gantz would provide them their mission and equipment before teleporting them to the target location. Similar to the apartment, the hunters were invisible to all bystanders in the area alongside the alien target though the affects of their attacks could be seen on the environment. The location was a square mile region that encompassed a square where the target alien was present. Hunters were not allowed to leave these areas and any attempt to do so would see an unknown form of energy being projected from orbit that caused the disobedient hunter's head to explode. The hunt needed to be done within a set timeframe that ranged from an hour to longer and though duplicated the hunters who died during the hunt died permanently. Any person slain during the hunt would be shown on Gantz surface where they would turn from a colored portrait to a black-and-white one indicating that they had died. If completed, the survivors of the hunt would be teleported back to the apartment with the sphere and even those that were badly wounded were restored completely in the process. All that remained was the presentation of scores to the contestants who were allowed to finally leave the apartment and return to their lives until the next hunt where they would be teleported back into the room once more with new candidates.
In terms of equipment, the racks within contained a number of tools for the Gantz hunters which included:
- Suit : these black form fitting suits could only be worn after removing all other clothing and were seemingly made to fit the specific wearers. The suits often made those unfamiliar with the hunts as being an otaku or cosplayer. In reality, they had a number of functions as the suits greatly improved the chances of survival during the hunt. Through singular focus, the suit greatly amplified the strength of the wearer allowing them to overpower physically strong aliens or perform massive jumps or provide greater endurance from physical blows. They also made the wearer somewhat immune to Gantz derived weaponry but did not provide complete invulnerability. A set charge was present in the suit's capabilities as eventually their power ran out that manifested as the spherical nodules at various points in the body popping with a blue liquid falling out whereupon the hunter lost all the enhanced traits provided by the equipment.
- Controller : these small pads were effectively radar systems used to track targets and displayed the information of both friends as well as foes. However, the readings given were not precise as they did not distinguish the target from the team mates but did display the boundaries of the hunting area that was the indicator for anyone that passed that threshold dying by Gantz's powers. In addition to the map, the controller also provided the countdown timer informing the user how long they had to complete their mission. A specific feature provided by these devices was the capacity to turn their user invisible to the naked eye though certain aliens were still able to track such hunters.
A number of weapons were also produced from Gantz with informal names given to them by the hunters selected by the sphere with this arsenal including:
- X-Gun : these pistol like weapons appeared as toys to those unfamiliar with them but actually were powerful guns with a large muzzle. These guns had two triggers that provided different firing modes and had a screen by the handle that provided an x-ray-like quality allowing the user to detect aliens disguised as inanimate objects by seeing their internal organs as well as skeletons. When both triggers were pressed, four points opened up by the muzzle giving an 'X'-like shape where a flash of light was projected. This was because the X-Gun did not fire projectiles but an unknown form of energy that appeared as a flash of light with a time delay before the damage came on the target. The effect on organic tissue saw flesh warp and deform before exploding at select locations with this being fatal on humanoid targets and damaging to larger foes.
- Y-Gun : another handgun with a lock-on ability that launched three 'laser anchors' connected to a rope in order to wrap around targets and securely pin them to the ground. With the anchors hooked onto the ground, the target was apprehended and could be sent back via the same transmission system used by the sphere to bring its selected hunters into the room. Both triggers needed to be pressed in order to fire the snare as the top trigger was used to get a lock whilst the bottom was used for initiating the send. Despite its capacity to trap targets, a strong enough target was able to break free from the net of the Y-Gun.
The hunts forced on the candidates by Gantz ultimately had a score for the number of deaths of target aliens. Each alien killed saw around 5 points being given to the person who made the kill shot. Upon reaching 100 points, a number of options were presented to the hunter by the sphere. These included the first being able to be free from the hunts and having all memory of Gantz being removed from their minds thus enjoying true freedom from the experience. Alternatively, a second option can be the sphere can offer the hunter access to weapon upgrades and superior arsenals for future hunts. A third option can see the sphere reviving a human that was slain during the hunt that was achieved through access to Gantz's memory. This was because the sphere also had access to the thumbnail prints of every hunter that appeared within the apartment room and even any human that was the target of a hunt.
- Kurono Kei :
- Kato Masaru :
- Kishimoto Kei :
- Izumi Shion :
- Sakuraoka Sei :
- Nishi Joichiro :
- Suzuki Yoshikazu :
- The sphere's origins are not mentioned in the Anime but shown briefly in the Manga.