Black Hole of Calcutta Monument

Origin
The Black Hole of Calcutta was a small dungeon in the old Fort William in Calcutta, India, where troops of the Nawab of Bengal, Siraj ud-Daulah, held British prisoners of war after the capture of the fort on 20 June 1756.

One of the prisoners, John Zephaniah Holwell, claimed that following the fall of the fort, British and Anglo-Indian soldiers and civilians were held overnight in conditions so cramped that many died from suffocation, heat exhaustion and crushing. He claimed that 123 prisoners died out of 146 held. However, the precise number of deaths, and the accuracy of Holell's claims, have been the subject of controversy.

Holwell had erected a tablet on the site of the 'Black Hole' to commemorate the victims but, at some point before 1822 (the precise date is uncertain), it disappeared.

Effects
When approached by any sentient entity, the monument will rise into the air and produce a kind of phantom replica of the original dungeon. After that, it will pull any living creatures into itself, and will continue to do so until it has either cleared the area, or more approach it. Once it has finished, the room will begin to become smaller until those inside either die of heat exhaustion, suffocation, or crushing.

Trivia

 * When it was first collected by Warehouse 12 agents in 1819, it was noted that the monument neither levitated nor created a room. Instead, it trapped those who approached it by teleporting them into the original dungeon. The room did not shrink, either. However, once collected, its new effects were made evident.