The modern XCOM: Enemy Unknown reboots this story for a new timeline. In the timeline of XCOM 2 , it is revealed that X-COM actually lost the war early on, and the "victory" from the previous game was a simulation run in the Commander's mind while they were held captive.
Once X-COM develops the (a powerful interstellar craft), they launch a final mission to Mars. UFO: Enemy Unknown
The ultimate goal is to destroy the Alien Brain , a massive bio-computer that serves as the mastermind and central hub for the invasion. The Endings The modern XCOM: Enemy Unknown reboots this story
Destroying the Alien Brain severs the link between the invaders and their leadership, causing the alien forces on Earth to collapse and saving humanity. The ultimate goal is to destroy the Alien
You discover that alien technology relies on Elerium-115 , a stable heavy element not found on Earth, which becomes the most vital resource for humanity's advanced crafts and weapons.