Before Crisis: Final Fantasy VII

He boasts an outstanding ability even among the 1st Class SOLDIERS, and he is known as the Silver SOLDIER. President Shinra puts a lot of trust in him and Sephiroth disagrees with anyone who opposes Shinra.

Crisis Core -Final Fantasy VII-

From the very start of the story he has already captivated many as a highly skilled SOLDIER, but it was with the Wutai War that his reputation as a hero was sealed. But behind the scenes, he is conflicted as he is assigned to track down Genesis and Angeal, his colleagues and his friends. One of the highlights of Crisis Core, is Sephiroth's portrayal as a genial human being.

But on a mission to Nibelheim, he discovers he is literally a tool of Shinra, and resolves to follow the path of an enemy to Shinra, and to all mankind.

Last Order: Final Fantasy VII

Tseng's recollection of the Nibelheim events, and the origin of Zack and Cloud's tragic fate. Setting Nibelheim ablaze and massacring the villagers along the way, Sephiroth heads to the Nibelheim Mako Reactor in an attempt to join his mother, Jenova.

Final Fantasy VII

Believed to have died five years ago in the Nibelheim Mako Reactor, he suddenly appeared in the Shinra Building and murdered President Shinra. He claimed to be heading towards The Promised Land, and guided Cloud to the Northern Crater. He synthesized with Jenova's cells to complete his revival, his goal was to control the Planet by means of directing the ultimate destructive magic, Meteor, towards it, but Cloud and company put an end to his plans.

Final Fantasy VII: Advent Children

Although he was defeated by Cloud, and had once fallen into a Mako Reactor, he did not return to the Planet but instead was diffused into the Lifestream. Elements from his body flowed into the atmosphere, and the rejection of these heterogeneous elements was called Geostigma. Soon after, a remnant of his called Kadaj acquired substance. He was to fulfill the volition inherited from Jenova to rule the Planet, and fought against his fated rival Cloud.