The Sephiroth sleeping in the Northern Crater was the real and original one controlling the whole thing through his consciousness / connection to Jenova. He was swept there by the lifestream when he fell into it from the Nibelheim reactor.

The Sephiroth you followed around from the Shinra building up to that point was Jenova (working together with Sephiroth) using her(its?) ability to appear as another person. This is why when you first meet Sephiroth on the Junon boat he doesn't recognise you, as Jenova hasn't had access to that part of Sephiroth's memory yet. This also explains away the very weird alternative idea of Sephiroth going around carrying that great big lump of flesh.

She also morphed into Tifa briefly to get whoever was holding the black materia to come and hand it to Cloud, before turning back into "Sephiroth" and then disappearing.

From the meteor summoning onwards you are only dealing with the real one, and you only meet up with him in the crater.


It's a teamwork thing, they're both just as evil.