Ether
The Ether, sometimes called the Ethereal Plane, lays in the Void and encompasses the rest of the universe. Within the Ether lies the Dream, within which lies the Veil where the various realms exist. The Ether is the ultimate source of all magic. Mana flows freely through the Ether, intermixing with the subconscious thoughts of the Dream. A Catalyst can tap mana directly from the Ether.
It is to the Ether that the souls of the dead go before they are reborn. If a Soul Mage seeks to resurrect someone who has been dead for too long, they must dredge their soul out of the Ether.
The Ether can be reached via teleportation ritual using the numerological key of 2. However, doing so will immediately kill anyone not skilled in Soul Magic. More commonly, the reverse is used to summon the dead who have not yet been reborn.