Time Crystals are important items in the TimeSplitters series of games. Time Crystals are used to travel through time and were used by TimeSplitters in TimeSplitters 2 in their quest to destroy humanity. Cortez must collect all nine Time Crystals so that the TimeSplitters cannot use them. In the end of the game, the crystals were taken from the space station by Cortez.
In Future Perfect, the time crystals are used in order to go back in time to prevent the TimeSplitters from ever being created. Crow also uses them in his time device while searching for immortality. He drilled for the crystals on the same island Cortez goes to in Scotland The Brave. The time crystals are destroyed at the end of Future Perfect.
Where Cortez manages to steal a raw form of the Time Crystals, Anya believes they were of outer space origin, possibly from an asteroid.