Jenova, or the Crisis From the Sky, came to the planet many years before Final Fantasy VII took place. It came disguised to look like the rest of the Cetra on the planet at the time, and spread diseases to them, killing off many Cetra. This was a threat to the planet, so the Weapons were called to fight it, but they were not needed. A few remaining Cetra were able to beat it.

Cloud and the team first meet Jenova at the Shinra lab, where it was being held. Sephiroth freed it and took it with him. He considered it his mother (he was injected with Jenova cells) and it was their destiny to rule the planet.

Always a tough boss, Jenova usually stands in the way of you and Sephiroth, but when you kill it in the bottom of the North Cave, you know that it is time for the final battle between you and Sephiroth.