Historia Crux

a gameplay element from a game

The Historia Crux (ヒストリ南十字座), known as Historiacross in Japan, is a gameplay and story element from Final Fantasy XIII-2. It allows players to travel between locations and visit them in different time periods. To unlock new places and time periods, the player needs to find Artefacts located all over the world. Visiting these areas at different times will give players access to new items, and it can also change the course of the game.

It is revealed that there will be opportunities to see characters at different ages, replay the game, and see multiple endings by utilizing this system. This will allow a fully powered team to fight any previous bosses from the game with much more of an advantage. Though the future can be visited, the events before or during Final Fantasy XIII cannot be revisited as this would cause a time paradox to ensue.

The date system is marked by the letters "AF," which stand for "After Fall."

Story
In the aftermath of the events that took place in Final Fantasy XIII, Lightning is captured by darkness from another world and dragged to the edge of time, thus written out of history. She falls through the Historia Crux, transported to Valhalla.

Three years later, Serah Farron travels with a mysterious young man named Noel Kreiss on a quest to rescue Lightning, and together they visit various time periods through the Historia Crux. When Serah asks Noel how he came to exist in her own time period, he reveals that it was because of the Historia Crux itself, and he explains to her what it is.

Etymology
Historia is Latin for "history", whilst Latin crux means "to intercept at a central point".