Entire Body: VvV Razor Trooper
Helmet: Sculpted
Chest unit: Spy Troops Depth Charge rebreather
Oxygen Tank: Stikfas Fireman accessories

I have always been a huge fan of the Gerry Anderson series UFO. When I saw the Razor Trooper figure, my immediate reaction was that I could use it to do an updated version of the alien. For those who don't know the series, it involved a secret military organization fighting an alien race who were coming to Earth and harvesting humans for spare part surgery to keep them alive. They pre-dated the bunch out of Star Trek Voyager by about twenty years. I have put a pic of the originals for comparison.