There is an old record, copied and recopied across more generations than its copiers could name, and it begins with two women who should have been enemies and were not.
One was an Infinite Lifeform. One was a Source Lifeform. By the laws of how things are and have always been, they were born to fight each other, the way the tide is born to oppose the shore, and they would likely have lived their whole long existences proving the laws correct, except that they met for the first time on the same day they each met a Primeval One, and a Primeval One does not care which of its prey hates the other.
The record does not say much about THE Primeval One. Records never says much about Primeval Ones.
It says only that the thing was foreign, that it was old in a way that made the two women feel young despite the ages each of them already carried, and that neither Infinity alone nor THE Primordial Source alone was enough to survive it.
