Duplicate

A Duplicate is an artificial lifeform created as an exact image of a living person in Final Fantasy XIII-2. The duplicate calls the person whom they were modelled after the "Original". Duplicates are able to teleport and appear and disappear as they will.

Datalog
''A duplicate is a human-like entity created by the Academy by scanning a person's molecular information and reproducing it as a solid model. It is basically a physical copy of that person, but incapable of independent thought—certain molecular functions cannot be reproduced, and are supplemented with approximate calculations.''

''Although possessed of a physical body, and some military-purpose models do exist, duplicates are essentially solid, three-dimensional images. For this reason, should a duplicate ever be disconnected for the network it would cease to exist.''

Story
Serah Farron and Noel Kreiss travel to Augusta Tower 200 AF to find out the truth behind the "forbidden history" they heard of in Academia 400 AF. They enter the tower and find it full of people who have no "presence" and act completely passive. They come across Alyssa Zaidelle's duplicate who explains to Noel and Serah what duplicates are. Serah wonders whether duplicated people still have "spirit", but Noel says the legends say that the Goddess Etro only bestows spirits to humans.

During an elevator ride with Alyssa's duplicate Noel and Serah enter a paradox and witness scenes from 187 years ago where Hope Estheim and the original Alyssa were murdered by the tower's artificial intelligence. After having taken control of the Academy the artificial intelligence wiped out the humans and created duplicates of the people involved to hide the event. This is the "forbidden history".

If one chooses to do an optional side quest in Bresha Ruins -005AF- to collect research notes for a scientist in the Academy, it is revealed that the notes contain detailed plans for both the Tower and the duplicates, which the scientist denies writing and is convinced the notes are from the future. This implies that the very existence of Augusta Tower may be either a paradox, or a Stable Time Loop.