Ozma was born in a time where Humanity lived alongside their creators, the brother Gods of Light and Darkness, and all could wield magic. Jinn described him as a great warrior that fought only for righteousness, and he was courageous and pure of heart. One day, Ozma set out on a quest to save a lone woman named Salem, who was locked away in a great tower. After the two escaped together, they fell in love and planned to spend the rest of their lives with each other traveling the world and going on adventures. However, Ozma soon fell ill and succumbed to his sickness.
Heartbroken and angry, Salem traveled to the Domain of Light where the God of Light dwelled. There, she pleaded with him to resurrect her love, but he refused. Desperate for help, she then traveled to the lair of the God of Darkness, explaining her plight and taking care not to mention her visit with his elder brother. Pleased with her apparent loyalty, the God of Darkness rewarded her by bringing Ozma back from the dead, who responded to his sudden resurrection with great distress and confusion. However, at that moment, the God of Light intervened and returned Ozma to the afterlife to preserve balance, only for his brother to revive him again. Salem had turned the Gods against each other, and as such the God of Darkness destroyed Ozma once more as punishment.
As Salem led the people of the world against the Gods, Ozma rested in the afterlife. After the Gods destroyed Humanity and abandoned the planet now known as Remnant, the God of Light offered Ozma the chance to return to the land of the living to act as a guide and protector for the new Humans. He also charged Ozma with protecting the newly-created Relics, powerful artifacts that once united would summon the brother gods back to Remnant to judge Humanity. The God of Light explained that until Ozma's task was complete, he would reincarnate by joining his own soul with that of another like-minded individual to ensure he would never be alone. Ozma accepted and returned to the world in a new incarnation.
The Pretend God
After returning to Remnant, Ozma met with an unfamiliar world. Cities were different, a race known as the Faunus shared the planet with Humanity and magic was nothing more than a myth. After hearing talk of a "Witch", Ozma traveled to a secluded cottage where he found and reunited with Salem. The two reconnected, though Ozma kept his deal with the God of Light and the existence of the Relics a secret. Salem convinced Ozma that as the only two magic-wielders left, they could act as Gods and could create a paradise the Gods never could. Together, they used their abilities to unite Humanity, created a prosperous kingdom and started a family.
As Salem's methods became more brutal and her disdain for the new Humans became apparent, Ozma began to show doubts. After discovering that their four daughters were capable of wielding magic, Ozma revealed his secrets to Salem and realized that the God of Light was right in that she was no longer the woman he originally fell in love with.
One night, Ozma attempted to escape with his daughters, but Salem stopped him. The two fought a ferocious battle, destroying their home and claiming the lives of their children in the process. Salem flipped Ozma on his stomach after he tried crawling to safety and stomped a foot on his chest. She condemned him for choosing his promise to the Gods over their family and love and burned him alive, and the centuries-long feud between the two former lovers began.
Ozma spent several of his incarnations in mourning, trying to forget the horrors of his past through seclusion and drinking.
Eventually, he accepted his duty to protect the world from Salem and learned to live alongside the souls he joined with. At least one of his incarnations had a family.
At some point, he apparently gifted a large amount of his magical power to four women who would become the first Maidens.
Eventually, Ozma sought out the Relic of Knowledge and asked Jinn how he could destroy Salem, and Jinn told him he could not, leading him to lose hope.
Thousands of years after his original time, Ozma's second-most-recent incarnation and the one most relevant to the plot of RWBY was Professor Ozpin, the Headmaster of Beacon Academy. By this point, Ozma had created a network of agents to assist in his war against Salem, including James Ironwood, Leonardo Lionheart, Glynda Goodwitch, the Headmaster of Shade Academy and several more, such as Team STRQ.
After his death at the Battle of Beacon, Ozma/Ozpin's soul joins with that of a farm boy from Mistral, Oscar Pine. Ozma and Oscar's souls are not yet fully combined and there is some animosity between the two at first, with Oscar showing distrust and contempt towards his predecessor on several occasions.
After retrieving the Relic of Knowledge during the Battle of Haven, Ozma begins the journey with Qrow, Team RWBY and what remains of Team JNPR to Atlas to secure the Relic. It is on this journey that Jinn, at the request of Ruby, reveals the truth of Ozma's past to his allies. With the full history revealed, Ozma/Ozpin withdraws deep into Oscar's mind where Oscar cannot find him, emerging only once to assist Oscar in landing a damaged Manta.