The Oraculum is a device in Dishonored 2 found in the Royal Conservatory of Karnaca during the mission The Royal Conservatory, and an important part of Delilah's plan to take over the Empire of the Isles.
Created during a collaboration between Kirin Jindosh and Breanna Ashworth, the Oraculum is part science and part magic. Its purpose is to listen in on the prophecies of the Sisters of the Oracular Order through the Void and influence them. The device mainly works by channeling the energies of the Void through effigies of the Sisters.
The engine is composed of parts of Overseer music boxes, and produces Void energies with their Ancient Music. The energy is then transmitted by coils through cables, which direct it to the effigies. The effigies themselves consist of exhumed bodies of the Sister of the Oracular Order, connected to the mind of their living successors. They are bound with various relics and artifacts to reinforce the connection, such as the Order's scarves to cover their eyes and their maces. Magic drawings complete the installation, which as it is gives a clear audio feedback of a Sister's thoughts when powered.
A single person, through their connection to the Void, can manipulate the energy feed to the effigies after attuning the device to them. A series of lenses focuses those energies, but faulty lenses can scatter these energies and even erode the person's link to the Void.
Delilah had Jindosh and Breanna build the Oraculum to manipulate the Abbey of the Everyman, and in turns the population of the Isles into worshiping her. She would use the device to influence the prophecies of the Oracular Order, which the Abbey fervently consult.
Ashworth resorted to exhuming bodies of the Sisters from an Abbey graveyard. The Sisters' minds are linked even through death, and acquiring hair or nail clippings was impossible. It took her nearly a month to complete the effigies and refine them to hear and influence the dreams of the living Sisters.
Jindosh completed his part of the work before the mission The Clockwork Mansion, and so his demise did not influence progress on the Oraculum. The original lenses he and Breanna devised were faulty, scattering the energies produced by the device and draining Breanna's connection to the Void. Breanna removed them and brought them to her workshop for study before destroying them. One of the witches brought them back there after hearing others planning to throw them in the ocean.
The protagonist first hears of the Oraculum and Breanna Ashworth from Anton Sokolov, who spied on Jindosh during his captivity. On the advice of Sokolov and Meagan Foster, they set on the Royal Conservatory to incapacitate Delilah's first lieutenant and stop their project.
The faulty lenses can be used to eliminate Breanna non-lethally by taking her powers from her. In order to do so, the lenses must be found and inserted to the Oraculum, which must then be activated by pulling the lever.
- If the lenses are not manipulated, pulling the lever allows the protagonist to listen to various of the oracular prophecies. The achievement Oracular Echoes is obtained by doing this four times.