That night, Aiden set out from the Rose Iron Prison, heading towards the Heretic Inquisition Bureau.
Having confirmed that the "Rebecca" he had been in contact with was actually Presia, he realized a lot of things.
The "token of the Great Witch" was probably swallowed forcibly by Rebecca before her memory got sealed, in order to pass the critical evidence to the Heretic Inquisition Bureau.
This act, to a certain degree, also saved Rebecca's life. After swapping bodies with Rebecca and locking away her memories, Presia could have simply killed the Rebecca trapped in her own body and be done with it.
But after Rebecca swallowed the token, Presia's options became limited. At that time, an entire squad was hunting down Presia—killing Rebecca and letting her body fall into the hands of the Heretic Inquisition Bureau would mean that, once an autopsy was performed, the token would end up with them.