The Noumenon (Labyrinth)

Exactly what the Noumenon is, has been the subject of considerable debate among Covenant scholars for centuries. Some believe that it is a part of the Halo Array, while others insist that it is separate, but equally important. Even its purpose is unknown, and speculation ranges from a massive Forerunner shipyard to a research facility, and even to a rival to the Ark. For a long time, even it's existence was uncertain - the only sources were obscure engravings copied from destroyed Forerunner relics from the Sangheili world of Ketesh, known for producing historical theologians who have been rejected by the Covenant as legitimate.
All that is known for certain is that the Noumenon is related to the Labyrinth Array in some way - whether as a small part, or a major factor. As such, its importance during the Mandorla Campaign is beyond dispute - the Covenant, Sangheili, UNSC and Flood never reached the Noumenon, though they did stumble across a number of Labyrinth Facility Worlds and the local Nexus Relay. For now, the Noumenon remains an obscure Forerunner area steeped in Covenant myth and rumour.
==Quotes==
* "On the one hand, you have the Prophet of Induction, who claims that it is located at the centre of the galaxy in the middle of the super black hole. On the other, Scholar Sunda 'Oldarkamee claims that it represents another plane of existence to be attained during the Great Journey. Nobody really knows what it is."
* "There are few who can deny that the Noumenon is important. Exactly why it is important, even the Forerunners were unclear about - the only texts that mention it have since been destroyed, but only said that the Labyrinth would lead to the Noumenon, and to infinity."
* "Apparently, a lot of the Brutes thought Mandorla itself was the Noumenon. Even the Prophet of Remembrance didn't realise that they weren't even close! Even after the Magus Incident, they never caught on that they were heading the wrong way entirely."
* "Some say even the Noumenon leads elsewhere. Jesus, just how far does the Labyrinth go?!"