Influenced by Sephiroth, Cloud becomes suspicious of his memories and insists he is not a real human, but instead a specimen created from Jenova's genetic material by Professor Hojo. Jenova was an interstellar creature who crash landed on the planet roughly 2,000 years prior to the game's events. Jenova had intended to infect all living organisms on the planet with a virus inducing insanity and monstrous transformations; among its victims were most of the Cetra. Attempting to defend itself, the planet created giant monsters called "WEAPONs". The majority of humans fled rather than fight Jenova; however, a small group of Cetra survivors managed to defeat and confine Jenova. Eventually, the remains of Jenova were unearthed by Professor Gast, a researcher for the Shinra Company. Mistaking the creature for a Cetra, Gast was given authorization to conduct an experiment to artificially produce a Cetra by combining cells from Jenova with the fetus of an unborn child. Sephiroth learned that he was the product of this experiment while on a Shinra mission in Cloud and Tifa's hometown, Nibelheim. He concluded that he was a Cetra who had been produced solely from Jenova's genetic material. He burned down Nibelheim, intending to kill all descendants of those he believed had abandoned his ancestors in the defense of the planet. Cloud confronted Sephiroth during this massacre, after which Sephiroth vanished under unknown circumstances and was presumed dead until his reappearance in the Shinra building. When AVALANCHE travels to the Northern Crater to confront Sephiroth, he tells Cloud that he was not in Nibelheim, showing him images of a SOLDIER with dark hair who occupies Cloud's place in his memories. Tifa is unable to refute Sephiroth's claims, and Sephiroth casts the Meteor spell, causing the planet to awaken the WEAPONs in response. During the earthquake that follows, Cloud is separated from his companions and falls into the Lifestream.