In a sprawling industrial site, a mix of open, dust-swept killing fields, claustrophobic hallways and obstacle-laden vehicle bays, 8-foot-tall mandibled aliens are cutting down team after team of Homo sapiens soldiers. Those aliens, called Elites, are not only larger than their opponents, they also possess force fields and advanced beam weapons that emit crackling blue and red plasma bolts. The Elites are among the toughest of the Covenant, a confederacy of alien species united under the banner of religious fanaticism and galaxy-spanning war.
But the humans who are fighting—and losing—are elite in their own right, cybernetic supersoldiers called Spartans. These commandos are decked out in their own force fields, which radiate from strength-enhancing powered armor. In the brutal calculus of this particular conflict, the aliens are stronger, but they should also catch more bullets and shrapnel from rockets and grenades. This is supposed to be a fair fight.