This dusty tome is filled with tight script by a wizard who names himself "Burke." By the writings within, it appears that this place was once his own home, and his experiments revolved around the creation of a permanent dimensional aperture through which he could summon and control planar creatures.
The wizard notes several times that High Captain Kurth wishes to use the aperture for his own purposes and has become quite demanding. This made the wizard nervous enough that he jotted down some thoughts on how to close the aperture, if necessary. He notes that he possesses a sphere filled with water from Celestia and a sample of abyssal metal elsewhere in his home. Placed together in the aperture, these would bring about the desired disruption.
His only concern about doing such a thing is that the magic that controlled the planar creatures summoned by the aperture would also be disrupted, resulting in chaos.