The Gersh Device can only be obtained through the Mystery Box for 950 points, and three are received when found. When thrown, it creates a small singularity that will slowly pull all the zombies that are present on the map towards it, killing them upon impact with the singularity, awarding the player 50 points per zombie. A player can dive or jump (but not walk or sprint) into the black hole, which will then teleport the player to a random location.
The Gersh Device takes up the player's tactical grenade slot. It is one of two tactical Grenades in Ascension, the other being the Matryoshka Dolls. It is also one of two tactical Grenades in Moon as well, the other being the QED. The player cannot possess both; if the player attempts to take Matryoshka Dolls or the QED, any remaining Gersh Devices will be swapped, and vice versa.
The Gersh Device is an extremely effective weapon to be drawn from the Mystery Box as it can kill a line of Zombies without hassle and gives the players a short break from the zombies. This weapon is also effective if one wants to revive a downed teammate without being attacked (similar to Monkey Bombs).
The Gersh Device is a major component of both the Casimir Mechanism and Richtofen's Grand Scheme Easter Eggs. In the Ascension Easter Egg, it helps to open a portal to free Gersh. In the Moon Easter Egg, it is used to bring the Casmir Mechanism's plates from Area 51 to moon, and also draws in the Vril Sphere.
In the story, Gersh and Yuri started working on the device, project Mercury, in December 12th, 1962. However, work on the device was halted and Yuri moved to work on rockets. After reading Richtofen's diary, Yuri is consumed by Samantha's voice, telling him to complete the Gersh devices, and he obeys. By Samantha's command, Yuri used the device against Gersh. The device trapped Gersh and sent Yuri to the Pentagon.
In Moon, the Gersh Device referred by Richtofen as a Casimir Mechanism. The Casimir Mechanism is based on the the Casimir Effect. The effect heavily revolves around the vacuum, one of the scientific interpretations of the Aether (Aether was believed to be the material that fills space in case of a vacuum/void) . In particular, Richtofen says during the Moon Easter Egg: "The Casimir effect only occurs when there is a vacuum". The Gersh device consists of two plates being close to each other as in the Casimir Effect (as well as in Moon's Casimir Mechanism from the Easter Egg)
When activated, it will start pulling every single zombie on the map, but since it only lasts 10 seconds, it will release them before pulling them in. Zombies closer to the device will be pulled more strongly.
Space Monkeys will run and jump into the black hole willingly. However, this only teleports them and does not kill them and will not give the player points when doing so.
If the player throws a Gersh Device at the ground whilst being in a complex that has multiple levels, the player will usually be teleported one story down.
According to the radios around the map, the Gersh Device was not originally meant to be used as a "black hole bomb", but as a portable teleporter.
When a Gersh Device is thrown outside of the playable area (excluding near the generator for the Casimir Mechanism, or the plates for Richtofen's Grand Scheme) the device will not activate and will not be refunded. While this happens, the player can hear Samantha laughing, just as when the Mystery Box moves.
Hellhounds are unaffected by this weapon. Astronaut Zombies are partly affected by it; they will be sucked towards it, but will not actually fall into the black hole.
If all players are inside Area 51's cage (activated when a player hacks the Pack-a-Punch Machine) the zombies will be completely unaffected by the Gersh Device, but if the player jumps into it they will still be teleported to a random spot in Area 51.
In one of Richtofen's quotes from Moon, he refers to the Gersh Device as a pocket teleporter, which is one of the items seen the Moon's loading screen.