ME?

Sephiroth is estimated to have been born around 30 years before the start of the game (exact year left unknown) to Professor Hojo and Lucrecia of Shinra. two Shinra employees, one of which was involved in the "Jenova Project", a study of the remains of a being known as Jenova. Wishing to study the effects of Jenova's cells on a human subject, Hojo and Lucrecia volunteered their unborn son for experimentation, who was henceforth injected with Jenova cells while still within the womb. After his birth, Sephiroth was raised by Shinra, having been told that "Jenova" was his mother, but with no knowledge of who or what Jenova was. With superhuman abilities gained from the Jenova Project experiments, Sephiroth showed inhuman strength and speed at an early age, Sephiroth became an elite member in SOLDIER, with the highlight of his career in the Midgar-Wutai war. A year after the war, he was aided by fellow 1st-Class SOLDIERs Zack Fair and Angeal in a mission to deal with the rogue SOLDIER Genesis, not trusting Angeal. Soon after completing the mission, both he and Zack were sent to investigate a Mako reactor at Nibelheim. It was there that Sephiroth discovered his horrifying origins as an experiment and integral role in the Jenova Project and misinterprated this to believe that he is the last Cetra and the humans were the cause of their "extinction". This information corrupted him to the point of emotionally driven madness, after which he destroyed the town and went to the reactor to release his "mother."

Zack pursued Sephiroth and arrived at the reactor in an attempt to stop him, only to be soundly defeated by his former comrade. While finally liberating Jenova, Sephiroth was caught off-guard and stabbed from behind by Cloud, who was armed with Zack's Buster Sword and a thirst for vengeance for what Sephiroth did to his home. Alive, although greatly weakened, Sephiroth exited the chamber carrying the severed head of Jenova. Cloud attempted to finish him off, although he got stabbed through the stomach. In the end, Sephiroth fell off the gangway and into the Lifestream below (while Final Fantasy VII has it that Cloud threw Sephiroth over the edge, Last Order had it that Sephiroth jumped off the reactor's edge of his own free will). Presumably thought dead, Sephiroth traveled the Lifestream, learning the truth of Jenova's nature, before ending up in the Northern Cave sealed in Mako while absorbing Jenova's head and the wisdom of the Cetra. Sephiroth hatched a plot to absorb, though physically unable, the planet's energy, and thus become a god.

Notions of Sephiroth's apparent death were put to question when Cloud and company were detained in Shin-Ra's headquarters. On the eve before a public execution, they escaped from their cell that had been opened very mysteriously. A trail of blood was left by a mysterious third party who had devastated the facility. Cloud found the President assassinated, impaled by a sword he confirmed belonged to Sephiroth. However, "Sephiroth" was actually Jenova's body taken over by Sephiroth's will and remolded in his image as his puppet in order to find and retrieve the "Sephiroth Clones", individuals who had undergone the same cell injection procedure as Sephiroth to prove Hojo's Jenova Reunion Theory.

Sephiroth's goal, revealed later in the Temple of the Ancients, was to drain the planet of its energy with the aid of the Black Materia and its cataclysmic power referred to as Meteor. Aerith Gainsborough, the last Cetra, attempted to stop him with the White Materia and its defensive power, Holy. Though Aerith succeeded in summoning Holy, Sephiroth appeared and killed her before she could fully activate it, leaving the White Materia active but unused. Cloud procured the Black Materia, but was emotionally manipulated against his will into relieving ownership of it to Sephiroth, who then cast Meteor and awaited its arrival within a sealed Northern Crater.

In the story's climax, the barrier was penetrated by Shinra's Mako cannon, allowing Cloud and the rest of AVALANCHE to descend into the Northern Crater to confront him. He first appeared to them as Bizzaro Sephiroth, before he molted out of his cocoon as Safer Sephiroth. With the destruction of his physical body, Sephiroth's spirit made a final mental assault upon Cloud within the Lifestream, attempting to overcome his will yet again and claim Cloud's body as his own. However, Cloud had already rediscovered himself and thus his inner strength had grown to the point where Sephiroth no longer had any influence over him. After an intense battle, Cloud finally overpowered Sephiroth, and banished his spirit back into the depths of the Lifestream.

Safer Sephiroth is the final form of Sephiroth seen in the original game. Though one more battle follows Safer Sephiroth's defeat, it is a scripted battle purely for plot purposes and cannot be lost, so the fight with Safer Sephiroth is essentially the final battle of the game as far as gameplay itself is concerned. It follows the battles with Jenova-SYNTHESIS and Bizarro Sephiroth, and after Safer Sephiroth is defeated, a staged battle, a lengthy final cutscene, and the credits follow.

The Safer Sephiroth battle is unexplained and leaves many questions unanswered, adding to Sephiroth's mystique and prompting much speculation about the battle's significance to the plot of Final Fantasy VII and its symbolic meaning. This has been speculated that the name "Safer" is a mistranslation of "Seraph", angels described in several religions, of which all depict the seraph as one of the highest ranks among angels. This would be consistent with his title

"One-Winged Angel".

It has been two years following the defeat of Sephiroth, and a disease called Geostigma has spread throughout the world, afflicting many with its ill symptoms of extreme fatigue and open sores on the skin. The now reclusive Cloud finds himself confronted by a strange trio of silver-haired brothers who are the Remnants of Sephiroth, the physical manifestations of Sephiroth's will and spiritual energy. His powerful will allowed him to endure the Lifestream and emerge from it before being fully diluted.[8]

Their leader, the youngest brother Kadaj, would later transform into Sephiroth after absorbing the contents of a case containing Jenova's remains. After his resurrection, Sephiroth reveals that he has been using Geostigma in a plan to corrupt the Lifestream and grant him control of the entire Planet. He would then crash it into another planet, thereby re-enacting Jenova's goal. He and Cloud then engage in their final duel, in which Sephiroth displays various powers surpassing those of other characters featured in the film such as flight, effortlessly slicing off and igniting a huge section of the Shinra building tower, and even calling forth the "tainted lifestream" with a mere wave of his hand to cover the sky. Despite being outmatched, Cloud finally defeats Sephiroth with his new Omnislash Version 5 Limit Break, causing him to fade away and leaving a mortally wounded Kadaj in his place. His final words to Cloud before dissipating, "I will... never be a memory" could be taken to mean that, despite his Remnants returning to the Lifestream and his spirit diluted, Sephiroth will never truly be gone and will continue to exist in one form or another.