Half-Life: Metamorphosis is an expansion pack styled mod for Valve Software's science fiction first-person shooter video game Half-Life, in the vein of Half-Life: Blue Shift and Half-Life: Opposing Force. Half-Life: Metamorphosis follows data analyst Holly Byrne at the time of the Resonance Cascade.
Expect some running and gunning in low grav across an armada of these. Don't question why they look so WW1 era, aliens are just mad retro like that.
It could be that the Xenians are Adapting Technology from other Races (Humans in this Case) for their own use like the Locust from Gears of War.