The Allies have detected weird energy sources coming from a Soviet facility. So Tanya was sent with some other Allied units

Alright, let's see what weird stuff these commies just did.

Little does she and all the other Allied forces know that the Soviets where testing their own Chronoshift and it opened several portals to another world bringing in, other factions (GDI, Nod and Scrin) as well as a weird mineral substance called Tiberium which is infecting the facility's perimeters