Encounter in Dragon Valley
Serpentine is first seen in Dragon Valley, aiding the Shuigang Helicopters in gunning down Torque's starship. He catches Torque, who patched together a Shellduck disguise, and interrogates him. Serpentine demanded to know how many Chasers were left, but Torque refused to talk, retreating into his shell. Furious, Serpentine wondered where the Snake Mount was, and saw parts of it falling behind him, as it was recently destroyed in battle. Serpentine decided to do things the hard way and attacks Torque, who escapes thanks to the timely arrival of Lilac.
Standoff in Shang Mu
Later, Serpentine intercepts Lilac in the Commercial District, in the city of Shang Mu. He attempts to dissuade her from getting in the conflict between Lord Brevon and the Chasers, telling that it wasn't her fight. Lilac then replied that it was the moment they brought to her Homeworld. Sepentine decides to make an attempt on Lilac's life, hoping that it will make Torque realize the consequences of his decision to allow Lilac and her friends to tag along. Unfortunately for him, he's no match for Lilac's strength, speed and skills. Not even his Robopanther was enough to defeat them. Nevertheless, Serpentine bought the Shuigang forces time to steal the Kingdom Stone, reminding the Commander and his allies of it. He tells them to "Enjoy their victory", just before escaping with the Sky Battalion.
Chasers Among Us
Serpentine contacts Brevon and tells him about the full moon in a cloudless sky, and to confirm that he has the Kingdom Stone. Brevon tells him to upload the scans and return immediately. Later, he attends a meeting with Brevon alongside Syntax, a brainwashed Prince Dail and several Shade Elites. Having learned that Torque have managed to survive and his new "pets" have joined him, Brevon decided that they must exterminate them before they foil his plans. However, the Commander and his allies have all been detained in Shang Tu by the Royal Magister, and it would be impossible to get to them without exposing their operations. So Brevon orders Serpentine to capture them and take them to their Remote Base as soon as they leave Shang Tu.
Torque is released from Shang Tu, and is soon captured by Syntax and the Absolution. Serpentine covers their escape by holding off Lilac, Carol & Milla with his Robogunship, but is once again defeated in battle by the heroines. His Gunship destroyed, Serpentine retreats to the Remote Base, in the outskirts of Jade Creek. It is there that he confronts Lilac, who infiltrates the Base alone to rescue Torque. She demands that he release Torque immediately, but Serpentine refused, stating he wanted Lilac nice and angry for what's as about to happen next. Lord Brevon enters the room and easily defeats Lilac with a single slash from his knife. Brevon then cuts off her ponytails and subjects her to electric torture, not only as a means of interrogating Torque, but to test his resolve and Lilac's determination.
Preparing for Liftoff
After the Remote Base is destroyed, Serpentine returns to the Dreadnought to help finish the preparations for the liftoff. They learn that Torque and his allies have managed to rally the armies of Shang Tu and Shang Mu in the Snowfields, and we're heading their way. Brevon gives the orders to Dail and his troops to fight against the united armies, and orders Serpentine to "Find the Commander and his pets and tear them to shreds". Serpentine goes with Brevon and his other forces as the Dreadought blasts off into space once more.
Serpentine's Last Stand
Later on, as Lilac and her friends make their way through the Dreadnought, they encounter Serpentine once again, but this time, he appears to be in critical condition. As they approach him, he suddenly transforms into a mutant monster to better fight them. Even so, he is defeated for the third time by the heroines, seemingly destroyed. During the end credits, Serpentine apears to be alive and back to normal, but is screaming in despair and disbelief over the loss of his robotic arms.
Seprentine survived the destruction of the Dreadnought, but failed to escape Avalice alongside the defeated Brevon. Marooned, he retreated into hiding and begun the long process of rebuilding his robotic arms. 2 years later, Serpentine continue to hide in a hidden location, waiting for the right opportunity to escape the planet and reunite with his master. Serpentine will fight the heroes at some point, but it's currently unknown if he'll face them in an act of vengeance, or is trying to avoid them.