"If you want to learn something about a science-fiction, alien-invasion shooter before playing it, just pay close attention to how it names its enemies. The single words developers choose to boil their interstellar or interdimensional threats down to often inadvertently reveal the character of the game beneath. Halo's Covenant and Flood conjure an aura of biblical scale and religious devotion. Half-Life 2's Combine suggests seamless integration and sleek, powerful technology. Killzone's Helghast sounds like grim, Germanic warmongering."