Oblivion is a boss that was first introduced in Turok 2: Seeds of Evil, and then featured as the main antagonist, and the final boss in Turok 3: Shadow of Oblivion. Oblivion is an ancient savage entity, a cosmic lifeform capable of devouring entire worlds, rendering them lifeless and barren. It is bent on destroying the Turok bloodline that protects the energy within the Light Burden; the only thing that ever caused it to feel pain. It also spawned a race called the Flesh Eaters; an army of lifeforms bound to Oblivion as a single entity, that carry out it's whims.
Before our universe was created, and before The Lost Land, there was Oblivion; a savage entity drifting through the cosmos like a monstrous, omnipotent jellyfish, Oblivion consumed every planet it came into contact with, invading the bodies of the living and devouring them from the inside, feeding off the very energies of the dead and dying. When the Primagen's Lightship was destroyed, the explosion created an energy surge triggering a chain reaction so powerful that the universe as it existed was completely destroyed. The resulting shockwave annihilated Oblivion's body, tearing it to shreds.
The moment the Lost Land was created, Oblivion first felt pain, and fear, and hatred. Life sprang forth in the wake of death, and a new universe was born; our universe. Oblivion survived. Though nearly obliterated by the pure energy source that would later be known as the Light Burden, Oblivion lived; and while regaining it's strength, began looking for a way to punch a hole through the netherscape that separates our world from the Lost Land, and the Lost Land from countless others.
The Turok line must die, so the Light Burden that carries the last traces of the energy that is it's bane will disappear, then chaos will befall the omniverse, and Oblivion can be completely reborn, and once again become the most powerful being that ever lived. According to Adon, Oblivion exists beyond the universe's fundamental forces of good and evil, light and dark, and order or chaos. She also reveals that previous Turoks have encountered it before.
Turok 2: Seeds of Evil
When The Primagen awoke, and launched his campaign against the Lazarus Concordance, Oblivion knew that his success would be quite convenient for it's own desires, and finally made a move, by placing fake Talisman chambers in every area that contained an Energy Totem, which would lead Joshua Fireseed into a dark, ominous area resembling Oblivion's Headquarters, where Oblivion Spawn laid in wait, ready to kill Josh on sight.
Turok 3: Shadow of Oblivion
In Turok 3, 2 years after Turok 2, Joshua was being tormented by dreams of Oblivion due to it's ever-nearing presence, which included images of a child being the key to salvation. Soon afterward Oblivion would make good on it's threats in Seeds Of Evil, when it finally breached Earth, sending the planet into chaos, immediately beginning to devour it's life force, but not before Oblivion's Sentinels appeared in the Fireseed family's home through temporal rifts, forcing Josh to sacrifice himself so Danielle and Joseph could escape.
When Danielle or Joseph destroy Oblivion's body, a small piece of it that makes up it's essence possessed Joshua's body, to make him fight as it's puppet. Adon defeating the infested Joshua, Danielle and Joseph destroyed Oblivion's Essence with the Light Burdens they carried, wiping it out for good.