The Mysterium Xarxes is both the gate and the key to Camoran's Paradise, and in a way it is Camoran's Paradise, literally. Mankar Camoran bound himself to the Xarxes and the book enables Martin Septim to open a portal. The book also holds various magical incantations and rituals, which can be used to open a portal to Paradise. However, this portal requires four artifacts to draw its power upon: a Great Welkynd Stone, a Great Sigil Stone, a daedric artifact, and the Blood of a Divine.
When all four objects are laid together, the invocation that the Mysterium Xarxes holds binds the four objects together, which results in the creation of a giant sphere of orange light and fire. This is the portal to Paradise. Once the Mysterium Xarxes is stolen from the Mythic Dawn cult at the Dagon Shrine and given to Martin Septim, the Hero of Kvatch is unable to carry the book again.
In The Elder Scrolls V: Skyrim, a single, scorched page of the Mysterium Xarxes appears behind a locked display case in the Mythic Dawn Museum in Dawnstar is all that remains. It is not explained how it ended up in Skyrim and cannot be obtained or read.
The first page of the Mysterium Xarxes translates as:
When I walk the earth again, the faithful among you shall receive your reward. To be set above all other mortals, forever. As for the rest, the weak shall be winnowed, the timid shall be cast down, the mighty shall tremble at my feet and pray for pardon.
The array of letters in the circle is not meant to be read with this text, it is a separate part:
Of bold Oblivion fire who finds you for Lord Dagon forever reborn in blood and fire from the waters from Oblivion.
The second page is instructions to build the portal to Paradise:
Come slow and bring four keys.
In my first arm, a storm. My second, the rush of plagued rain. The third, the tinder of Anu. The fourth, the very eyes of Padhome.
Master akin Master, mother is miasma to Destroyer.
Inside the triangle it says: