Eon is the offspring of Eternity and the Cosmic Axis. Eon has existed for eight billion years subsisting on the background radiation left over from the Big Bang. Eon was charged with nurturing the evolution of sentient life of the universe and to maintain conditions favorable for life in the universe. As such, early on Eon came to the conclusion that sentient life in the universe would require a protector. To that end Eon saw to the construction of the Quantum Bands. Eon is one of the few entities who posseses Cosmic Awareness in it's entirety, it is thought that this awareness can cause madness in a lesser entity.
Over the millennia Eon has chosen a legion of entities to bear the Quantum Bands and carry the title of Protector of the Universe as the need arose. The first of these was known as Glakandar the Stygian Starbender. Perhaps the most famous Protector was Captain Mar-Vell of the Kree, who ended the threat of Thanos as he attempted to use the Cosmic Cube for universal domination.
Roughly 200,000 years ago in the aftermath of the Titan Schism, Eon (along with Kronos) presided over the wedding of Mentor and Sui-San. Eon allowed the Quantum-Bands to be used as the rings to symbolize their union and the missing link in Eternal physiology to allow natural procreation between them. The fruit of that union was Thanos of Titan. After Thanos' nature could not be ignored and he murdered his own mother, Mentor returned the Bands to Kronos who declared (on behalf of Eon presumably) that the Quantum Bands would always oppose Thanos.
Eon’s last Protector was an Earthman, Wendell Vaughn, also known as Quasar. Who attempted to defend Eon against the Cosmic Assassin, Maelstrom. Quasar failed in this, forced to kill Eon himself in a vain attempt to protect the secrets of Cosmic Awareness. Quasar ultimately prevailed over Maelstrom and saw him destroyed.
Eon’s legacy was taken up by Eon’s daughter, Epoch.
Eon was dispatched and had his identity stolen by his evil son Era. Eon went to the White Room with the other Protectors of the Universe.