The Hydra's Gate History Society was a group founded on Earth to explore the history of Hydra Hall.
Around February 2022, the society held a ghost tour of Hydra Hall that was open to the public, which the Thirteenth Doctor, Yaz, and Dan noticed while investigating a string of disappearances. Later, with the disappearances solved by closing the portal to a pocket universe under the hall, Sidney Bird held a society talk at Hydra Hall about his life as an evacuee at the hall during World War II. (COMIC: Hydra's Gate)