XCOM is a rebooted turn based strategy game developed by Firaxis Games and published by 2K Games. The rebooted universe consists of three games (XCOM Enemy Unknown/Within, XCOM 2 and The Bureau: XCOM Declassified (a third-person shooter with an emphasis on squad-based tactics)) plus a tie-in comic detailing the events leading up to XCOM 2.
The plot of XCOM Enemy Unknown takes place on Earth as an unforeseen threat emerges from the skies of the Earth. The Commander (You) takes charge of stopping the alien threat by foiling their schemes to abduct and terrorize Earth's population. This is done by slaying the alien hordes, researching new technology that will "forever" change humanity, by levelling up your soldiers to gain access to new abilities, and customizing your soldiers to look like your best friends, only for them to eat plasma, after missing a 99% shot. (That's XCOM baby!)
The Enemy Within expansion brings forth an organisation called E.X.A.L.T, a shadowy organisation who are attempting to seize power by using the invasion as a distraction. The expansion also brings forth the ability to convert your troopers to cyborgs and genetically modify your troopers using the new mysterious substance known as "Meld".
In XCOM 2 it is assumed that the XCOM project failed within the first few months and the council of nations made a pact with the aliens. 20 years later the commander is then rescued and then brought back to "the Avenger", a helicarrier that was once an alien ship. It is again the job of the commander to fight the alien forces as well as ADVENT who appear to humans. As XCOM is no longer supported by the new governments, XCOM is now a rogue organisation and will have to get help from the resistance to help reveal the aliens wrong doings (although maybe there's a reason for their wrong doings).
Powers of the Verse
The main focus of the verse is the psionic energy (that can be researched by XCOM) by researching Psionic alien units. The psionic potential of a soldier is measured by the soldiers will (more will equals a better chance at using the abilities on foes). The troopers can temporarily control even the most powerful aliens in the game when fully upgraded, as well as using their abilities to: create a temporary indestructible shield, drain life from foes, create a deadly psionic storm that does heavy damage to anyone inside it, and much more.
The XCOM troopers themselves are hand picked from the best from around the world and later gain experience, as they kill more and more aliens. Once they hit the Colonel rank, they are fully skilled in a specific class. XCOM are able to research and fabricate technology from whatever they can get their hands on, which allows them to modify any design to suit their needs. In XCOM EU, they were able to design a Fusion Lance that was easily able to take out an enemy battleship in two shots. In XCOM EU they also designed a customized UFO that is 3 times faster than a modern day jet plane and 5 times more durable.
The Meld genetic modifications in XCOM EW allowed the troopers to have abilities like: superhuman leg strength, complete immunity to mind attacks, invisibility, regenerative abilities, detection to cloaked enemy units, and much more. The MEC Troopers also have many abilities such as: regenerative powers, jetboot modules, damage resistant buffs, plus much more.
The alien faction are capable of FTL travel and is a combined race of all of the conquered species captured by the Ethereals. Their main ship in XCOM EU/EW was untouchable even by XCOM's most advanced ships, and when it was about to self destruct, it was going to create a miniature black hole.