Though the original purpose of this location was lost to time, there were evidence of restraints suggesting its use as a place of confinement.
At some point the Isu structure was discovered by the ancient Britons that inhabited England, who also discovered other similar sites. The Britons decided to use these locations as tombs for their heroes who opposed and led the defense of Britain against the Roman Republic and later the Roman Empire.
By the time of the reign of Emperor Nero, the Britons had taken to gathering at the tomb as if at a sacred shrine, fomenting rebellion against Rome. Nero ordered engineer Manius Calvisius to make access to the tombs difficult but without sealing them away or defiling them, for doing so would bring a storm of ill fortune upon Nero, according to his soothsayer. Manius thus built a number of traps and puzzles across the tombs in an attempt to prevent anyone from entering and claiming the artifacts within.
In the late 9th century, Hildiran's explorations led her to a cell within the tomb. She meditated and heard voices of the past, leading her to believe the legends her mother told her, that her long-ago forebear had been imprisioned there, were true. She would return to the prison cell from time to time to think of her mother.
Around the same time, Viking shieldmaiden Eivor Varinsdottir of the Raven Clan traversed the tomb, avoiding the traps and solving the puzzles constructed by Manius, as well as retrieving a strange artifact and the Fallen Hero Helmet.