Proving Grounds addon - C&C4: Tiberian Twilight

In the year 2062, humanity found itself on the brink of extinction. Tiberium, the mysterious, alien crystalline structure that infested Earth for decades and caused years of relentless conflict between the Global Defense Initiative (GDI) and the Brotherhood of Nod, was close to rendering the planet uninhabitable. In the midst of this crisis, Kane, Nod's prophetic leader, emerged from seclusion to deliver GDI the message that he had developed a system that could control Tiberium and harness its power. But he could not build this "Tiberium Control Network" without GDI's cooperation. Thus, the two opposing factions—GDI and Nod—found themselves in a desperate and unlikely alliance to stop Tiberium from extinguishing mankind.