Sephiroth

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It was originally spun out of a portion of a Wikipedia article found here.
 
Sephiroth biography:
 
Sephiroth was born 25 to 30 years before the start of the game to Professor Hojo and Lucrecia of Shin-Ra. (Though some fans previously believed that Sephiroth was the son of Vincent Valentine—who was in love with Lucrecia—the FFVII Ultimania Guide confirms that he is the son of Hojo, as does Hojo himself during the game). Raised by Shinra with knowledge of Jenova as his mother, but without knowing what Jenova was, Sephiroth became a top-member in SOLDIER, with the highlight of his career in the Midgar/Wutai war.
 
A year after the war, during a mission to check on a Mako reactor at Nibelheim, Sephiroth discovered his horrifying origins as an experiment and integral role in the Jenova Project. This information corrupts him and drives him insane, after which he lays waste to the town and proceeds to the reactor to release his "mother." Zack, a fellow 1st class SOLDIER, arrives at the reactor to stop Sephiroth, but is sent reeling from Jenova's chamber after confronting him. While finally liberating Jenova, Sephiroth is caught off-guard and stabbed by Cloud, armed with Zack's Buster Sword. Sephiroth limps from the chamber carrying the severed head of Jenova, when Cloud attempts to finish him off. Sephiroth impales Cloud with the Masamune, but Cloud manages to throw him off the edge of the reactor into the Lifestream.
 
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. But though physically unable, Sephiroth hatched a plot to absorb the planet's energy, turning himself into a "god."
 
Notions of Sephiroth's apparent death are put to question when Cloud and company are detained in Shin-Ra's headquarters. On the eve before a public execution, they escape, aided by a mysterious third party who has devastated the facility. Cloud finds the Shin-Ra president assassinated, impaled by a sword for which he confirms its belonging 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 get the "Sephiroth Copies", members of SOLDIER injected with Jenova's cells to make them as powerful as him, to have the Reunion in the Northern Cave.
Sephiroth, seconds after fatally impaling Aerith. Screenshot from Final Fantasy VII.
Sephiroth, seconds after fatally impaling Aerith. Screenshot from Final Fantasy VII.
 
Sephiroth's goal, as revealed later by Bugenhagen, is to sap the planet of its Lifestream with the aid of the Black Materia and its cataclysmic power referred to as Meteor. Aerith attempted to stop him with the White Materia and its defensive power, Holy. Though she suceeded, Aerith was murdered by Sephiroth, leaving the White Materia active but unused. Cloud procures the Black Materia but is emotionally manipulated against his will into relieving ownership. Sephiroth called forth Meteor and awaited its arrival within a sealed Northern Crater.
 
In the story's climax, the barrier is penetrated by Shin-Ra, thus allowing Cloud and the rest of AVALANCHE to descend into the Northern Crater and fight 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 overcomes Sephiroth in the mental duel and banishes his spirit back to the Planet's collective of life energy