A Complete Guide to the Cosmos - Power to the Athanatoi! (Part One)
by Giulio CarolettiAfter the Birth of the Universes, the Ulterior Ones and the Mirror Gods would be known in the Normal Tetraspace with the common name of Outer Beings, although the purposes of the two groups differ greatly. In the Normal Tetraspace, meanwhile, the True Gods were taking steps to insure the preservation of the part of the Cosmos that they controlled.
The True Gods agreed to split the Normal Tetraspace in many smaller parts, separated from each other. To do so, they used an incredible amount of energy to bend the newly discovered Vortex's extremities. Although they tried to divide the parts completely, to prevent any contact between each part (named Multiverse), they didn't manage to separate them completely, and they continued to share a region, that would become known as the Inner Planes. Their continual effort, however, resulted in the birth of the Elemental Planes and of the common Ethereal, and the confinement of the ability to forge new "thoughts" in a small area of each Multiverse - its Prime Plane.
When the True Gods did this, they also told the Athanatoi, their closest servants, that they would retire from the Tetraspace and give them the duty to watch over the Multiverse. To insure that part of the Tetraspace would survive even if the Athanatoi failed to defend it from possible attacks from Outer Beings, however, the True Gods didn't tell any of the Athanatoi of the "splitting" of the Tetraspace, separating the Athanatoi from each other and putting only some of them on each Multiverse. So even the oldest Immortals on Mystara, as an example, don't know the truth, fooled by their former masters. Moreover, not all of the True Gods "retired" from the Multiverses: many assumed the form of new Athanatoi, or of Athanatoi that had died during the Battle, and in this disguise they continued since then to influence and control directly the Athanatoi.