During Samus's mission on Tallon Overworld she managed to find a suit upgrade known as the Phazon suit. During her final battle with Metroid prime which she defeated. The dying creature shot a tentacle into her and ripped the phazon suit from Samus. Minutes after the Phazon mine completely fell to rubble one thing became reality. A hand with an eyeball shot through the Phazon pit and stepped out of it. The blue liquid Phazon slowly fell of and the giant blackend figure stood tall. Tentacles grew from its body and phazon chunks glew in the dark caveren. The creatures breathing was heavy and it looked up. "Raghgggggghhhhgghgh!" The creature yelled out.
This creature was indeed not Dark Samus, but Sentinel Prime (Male counter part of Dark Samus."
The creature had more bulk and a rather large and just jacked up left arm. This creature sadly died and the Phazon pitt ate the corpse up to create Dark Samus. This figure was created by tons and tons of black/ grey paint and was a some what tricky one at that.