Following the failure in destroying the rogue giant robot known as the Mondo Bot, Jack finds himself in an underground sewer, where the peaceful human-sized robots are surrounding. A robot told Jack that their city of robots, Andromeda, is being destroyed by Mondo-Bot and that they built there over a magical, sunken city of giants. While the robots are believing Jack to become the key for awakening one of the giants, the friendly robots give him a breathing apparatus and send him into the city of giants to specify which one is fit to him. Jack finally found a giant samurai robot called the Robo-Samurai, which is made of stone and absorbs him into itself and comes alive. During the intense clash between the two giant robots, the Robo-Samurai defeats Mondo-Bot and goes back to the sea, releasing Jack from inside of it.
In the series' season finale, the Robo-Samurai later appears controlled by the robotic inhabitants of Andromeda, who came to save Jack from the death by Aku with the heroic support of everyone from the previous episodes Jack has met. It briefly fought Aku by giving him a beating and damaging. If Aku rained a hailstorm against the army of Jack's former allies, the robot endured the assault against him, but its robotic occupants and pilots were hopelessly killed.
No matter how the past destruction of Aku affected its existence, not to mention the inhabitants of Andromeda as usual.
Compared to Mondo-Bot and the robots of Andromeda, the Robo-Samurai is naturally mystical, being made of stone and absorbs Jack into itself with optical energy beams from its eyes. During Mondo-Bot's initial assault, it is also highly resilient to conventional weaponry and laser fire, suffering minor external damage and getting unharmed when its backfiring cannon is destroyed by the explosion.
A large Katana is the primary weapon of the Robot-Samurai. However, at the other hand, it exhibits proficiency in close combat. It likely features Jack's skills, but less effective than its pilot due to its sheer size. Yet, its opponent is similarly hindered and it allows Jack to perform martial arts to their full potential against it in battle.