Xion (BD)

Xion is one of the main characters of Kingdom Hearts II: Broken Destiny. She only appears as herself in the prolouge, after which she appears as the Sora.

Prolouge
Xion's backstory is the exact same as in the games up until the point she and Roxas fight. Roxas fails to defeat her and is absorbed, causing her to transform into a perfect replica of Sora, the process causing all of her memories to be erased.