Onder de naam XCOM: Enemy Within ontwikkelde Firaxis Games een grootschalige uitbreiding voor XCOM: Enemy Unknown. De game bewaart de kerngameplay van zijn voorganger, maar brengt onder andere nieuwe upgrades, wapens, verhaallijnen en multiplayermaps. 
            De game bevat ook een nieuwe set Trophies, er zijn er 31 te verdienen. 
	You Win (Platinum) 
You Win, Everything 
  
 	Who Needs Limbs? (Bronze) 
Augment a soldier in single player 
  
 	A Little Bit Alien (Bronze) 
Modify a soldier in single player 
  
 	Enemy Within (Silver) 
Get a Soldier to have 5 modifications in single player 
  
 	Steel Martyr (Silver) 
Deploy three tactical subsystems on a single soldier in single player 
  
 	Apotheosis Denied (Gold) 
Deal with the newest global threat 
  
 	They Shall Not Pass (Bronze) 
Eliminate all alien waves 
  
 	Zom-B-Gone (Bronze) 
Eradicate the infestation 
  
 	An Army of Four (Gold) 
Beat the game without buying a Squad Size upgrade on Classic or Impossible difficulty 
  
 	The Meld Squad (Bronze) 
Field a fully enhanced squad and win the mission 
  
 	Shieldbuster (Bronze) 
Eliminate an enemy's shield and kill it on the same turn in single player 
  
 	Someone Your Own Size (Bronze) 
Kill a Muton Berserker in melee combat in single player 
  
 	Taking a Load Off (Bronze) 
Stop a squad member from suffocating in single player 
  
 	Where in the World (Gold) 
Make certain of the new threat's location 
  
 	Mind the Step (Bronze) 
Jump two stories in one move in single player 
  
 	Nice Cover (Bronze) 
Use Collateral Damage to blow up a car in single player 
  
 	By Our Powers Combined (Gold) 
Field a squad with 4 augmented soldiers, each with a different base ability and win the mission 
  
 	Rise of the Machines (Silver) 
Field a squad consisting entirely of augmented soldiers and SHIVs (min. 4) and win the mission 
  
 	Mutatis Mutandis (Bronze) 
Field a squad where all members have at least two modifications (min. 4) and win the mission 
  
 	Mental Minefield (Silver) 
Kill an enemy as it is psionically attacking you in single player 
  
 	Anger Management (Bronze) 
Proc Combat Rush on the entire squad (min. 4) 
  
 	Remington... Max Remington (Silver) 
Have your special-duty soldier kill three enemies in the same mission 
  
 	G'day (Bronze) 
Kill an elite enemy Sniper with one of your own snipers in single player 
  
 	Regenerate This (Bronze) 
Kill an elite enemy Medic with explosive damage in single player 
  
 	Tingling Sensation (Silver) 
Kill an unseen enemy detected by a specially modified soldier in single player 
  
 	Pain in the Neck (Silver) 
Cause an enemy to suicide 
  
 	Solid Prospect (Bronze) 
Complete Deluge 
  
 	Ours are the Furies (Silver) 
Complete Furies 
  
 	Elite Defense (Silver) 
Beat a new special mission without losing any assets 
  
 	Guardian of Earth (Gold) 
Designate a highly decorated soldier as the Volunteer 
  
 	All Hands On Deck (Bronze) 
Get at least 4 kills with XCOM Base Security personnel 
 
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