Several hundred years passed since the original events of killzone 1, 2, 3 and Shadow Fall. UCN is stronger than ever, but extremely paranoid, being an almost-fascist like entity willing to conserve its colonies at all cost. But when an alien structure on mars is discovered, the colonies and Earth are more united than ever before in fear of alien invasion.

Nobody wanted to believe they were already here. But they are. The reapers had returned, and it was time they consumed all. Join Commander Shepard on the ultimate journey to stop the reapers, crossing paths with many other legendary heroes. Filled to the brim with gunfights, shout-outs and high octane action, relive the legend of The Shepard... the way it should have been.

One man can change an event with his tools. However if the one man changed something he will create a ripple effect. That ripple effect will burn the sins of the guilty. For all shall be cleansed in the gas of the Helghast.

After the Second Extrasolar War, mankind have experienced a revolution that reformed their interstellar 'empire.' From the UCN to the USN, mankind has now evolved to a new level. After decades of peace, one discovery will change it all.