No one knows where An came from exactly, but it seems that on one fine day, the Black Castle Ruins of the Radiant Garden had been rebuilt by a team of Heartless, led by a pale blonde going by the name of An Djinn. Aerith, who was investigating, was quickly shot out of the area, and a barrier formed around the Castle.
Sora had met An before back in Agrabah, and had fought her in exchange for information. However, despite "winning" the battle, Sora had to wait a few months until he could see her again, which she then says:
"Keyblades are an amazing weapon, and their original creation had dated back to tens of thousands of years. The Guardians, along with their Divine Blacksmith, pretty much helped shape battle history."
After explaining some other things, she fights Penn in a one-on-one battle and ends up losing. Her last words just before disintegrating were,
"May the spirit of Neltrédon strike you down."
