Scorpius is the half-Sebacean, half-Scarran Peacekeeper, and the primary antagonist of the series, relentlessly pursuing John Crichton for the secrets of wormhole technology locked in John Crichton's unconscious mind to create a wormhole weapon. He is the product of an experiment by the Scarrans – his Sebacean mother was raped by a Scarran to see if there would be any benefit in a hybrid. Raised by Scarrans, he has come to hate them, to reject his Scarran side, and to live for revenge against them. His physical attributes and his character traits are influenced by his race. Being half Scarran, Scorpius's body produces an extreme amount of body heat, particularly when angry. However, being also half-Sebacean means that too much heat will kill him. To prevent this he wears a full-body cooling suit notable mostly for the interchangeable cooling rods inside his cranium that absorb his excess body heat. He can see temperature gradients, especially of the face, allowing him to tell when people are lying. As a result, John Crichton was forced to enlist the use of herbal drugs to mask his love for Aeryn Sun for fear that he may use that knowledge against them to further his agenda.
Scorpius prides himself on his patience and his intellect. Scorpius is willing to do absolutely anything to achieve his goals, which he is very honest about when it suits him. He will lie, kill in cold blood, order the deaths of multitudes, torture innocents, and sacrifice those close to him to get what he wants. He is also willing to aid his enemies or humiliate himself if it will further his goals. He has returned from supposedly fatal situations more than once, which he credits to his "foresight and preparation". He manipulates others to do his work but does much on his own; his obsession with Crichton and his wormhole secrets is proof of that. He is highly educated and extremely intelligent, and exercises remarkable ingenuity. Only he knows how deep his schemes run and, while he claims his main desire is to eliminate the Scarran threat, protagonist John Crichton is loath to ever trust him.
His rank is never mentioned, and it is assumed that he does not officially hold one. Dominar Rygel XVI once claimed that Scorpius was "higher even than a captain," the claim was made more as a boast in an attempt to inflate Scorpius' value to kidnappers. His authority is not absolute, however, as Commandant Mele-On Grayza informed him when she superseded it. He is shown to have the authority to command a research base, a command carrier, a fleet of command carriers, and an even larger fleet during The Peacekeeper Wars.
Despite being an antagonist, Scorpius joins the crew of Moya to protect Crichton after his Command Carrier is destroyed and he is hunted by the Peacekeepers. He becomes a more or less trustworthy crewmember though he looks for any chance to get Crichton's knowledge and forms a relationship with Sikozu. In the end, he returns to the Peacekeepers and in The Peacekeeper Wars, instigates a war between them and the Scarrens. At the end of The Peacekeeper Wars he finally gets what he wants when Crichton uses a wormhole weapon on the Scarrens and Peacekeepers and is horrified, calling it "madness", finally understanding the danger of what he sought. He is last seen on Moya smiling as the Scarrens and Peacekeepers sign a peace treaty.