Tiberium, known as Ichor to the Scrin, is a fictional substance that is central to the plot of much of the Command & Conquer series of real-time strategy computer games. Within each title set in the Tiberium story arc (Tiberian Dawn, Tiberian Sun, Renegade, Tiberium Wars, Tiberian Twilight, and their expansion packs), the Tiberium crystals represent both the tools and spoils of war and are used by players to purchase new units and buildings, with each of the series' factions either directly or indirectly battling for control over the crystals. Tiberium has extraterrestrial origins and comes in a variety of forms, mostly the common green crystal but also the more rare blue crystals, the extremely rare red crystals, and in "veins". It was also demonstrated in a liquid form by the time of Tiberium Wars. Parts of the chemical composition of tiberium remain unknown.