When Forge, Maxwell and Steel were inside of the Makino Destroyer, Steel decided to stay with the ship and join Makino's forces despite Max and Forge's protests. Suddenly, a giant centipede monster appeared and Forge threw both of them out of the ship. At the same time, Kat Ryan and Jefferson Smith attacked the ship and it blew up, making Max, Steel and other N-Tek agents mislead that Forge was killed in the process. However, it turns out that he was alive and he had lost his left arm because the monster ate it.
Afterwards, Berto built a new robotic arm for Forge by the end of Earth Under Siege Part Two. Initially, he had problems controlling the arm due to the fact that it was still adapting with Forge's thoughts, but eventually he gained perfect control over it.
Forge's robotic arm gives him superhuman strength, as he was capable of crushing Jason Naught's arm, on his robot form, with ease.