Elder beings that are the oldest of all races. The First Gods exist as conceptional axioms of pure energy, beyond simplistic mortal notions of time and space.
In some ways it can be argued that they are nothing but willpower given form, or the Power Cosmic made manifest as awareness. Whatever they are, their fundamental nature is nigh-incomprehensible. When the universe first folded into existence, the First Gods arranged themselves not just as waveforms of power but abstractions of consciousness. The most potent of them embraced conceptual identities that resonated through all time and space. These ideologues became Eternity, Oblivion, Death, and Infinity. Others came into existence as consciousness manifested itself, including the Phoenix Force, Galactus, and the Endless and the ideologuic Entities of the Emotional Electromagnetic Spectrum.
In the time of the First Firmament, the First Gods were caught up in the war between Oa and the Celestials. Their home in Hyperspace was destroyed by Oan weapons, and the First Gods fled in infinite directions in our reality at the speed of thought while the universe shattered into infinite P-brane multiverses.
The God Races
'First Gods' refers to those entities that were present during the collapse of the First Firmament. The First Gods who later settled in the Demiurge later became known as the Elder Gods. The wave of their children following the creation of the Demiurge are the New Gods.
References to Old Gods refers to the refugee First Gods who were killed, or fled to Nullspace. They are also known as Great Old Ones-- Yog-Sothoth and C'thulu are two of the more well-known among their many numbers.