Turns beings into Werewolf slaves
The Arch was a magical gateway made up out of bones that existed sometime around the year 2351. Fangster managed to locate The Lost Bone of the Werewolf, which was burried in the wasteland not far from the Arch. By replacing a specific bone located in the side of the Arch with the Lost Bone of the Werewolf, Fangster activated the Arch. This way, when a series of dogs that Fangster had captured earlier passed through the Arch one by one, they turned into 'Werewolf Slaves' that lived to do Fangsters bidding. Eddie Spenser Jr. also passed through the Arch and began having Werewolf features soon thereafter.
Eddie managed to escape back in time to fetch the other Ghostbusters. Their plan was to remove the Lost Bone of the Werewolf from the Arch in the hope that by doing so, the curse of the Werewolf would disappear from the stray dogs as well as Eddie. Prime Evil ordered Mysteria to engulf the Arch in her magic mist to make it near impossible for the Ghostbusters to locate the correct bone. Luckilly, Corky's dog saved the day by sniffing out the correct bone.
As expected, the curse of the Werewolf was lifted and the entire Arch disappeared. Back at Ghost Command, Belfry found a new home for the Lost Bone of the Werewolf: on top of Ansabone, acting as it's receiver.
The Arch first appeared in the episode Doggone Werewolf.