Recusant's Sigil

The Recusant's Sigil (異端の印) is a symbol designed by Xehanort to represent the rejection of a Nobody from his original persona. It is incorporated into the new names of each of the original members of Organization XIII, and is derived from Xehanort's sleeping memories of the χ-blade.

In order for Xehanort to track his movements in the Sleeping Worlds, Sora was marked with the Recusant's Sigil, which took the form of a silver "X" on his shirt.