Proto Nidus Warframe 1999 fan art
You may ask why the arm? Well, the idea came from his prime version, he has a Golden arm for some reason. It gave me an idea, what if Nidus was someone who got infected by the infestation and had to cut off his right arm cause it was where the infestation started, but it turned out that the infestation was still spreading in his body, and he then attached the prosthetic arm with a vaccine to cure the infestation but only managed to maintain it, so that he doesn't lose his humanity.
You may ask why the arm? Well, the idea came from his prime version, he has a Golden arm for some reason. It gave me an idea, what if Nidus was someone who got infected by the infestation and had to cut off his right arm cause it was where the infestation started, but it turned out that the infestation was still spreading in his body, and he then attached the prosthetic arm with a vaccine to cure the infestation but only managed to maintain it, so that he doesn't lose his humanity.