A frightening, black-leather clad prescence, with a face like a skull, the half-breed Scorpius has proved to be Crichton�s worst adversary so far.

The product of a Scarran experiment, Scorpius is half-Sebacean and half-Scarran. These two clashing physiologies � one sensitive to cold, one to heat, have to be regulated by a coolant rod implanted deep in his brain.

His unusual origins explain much of his motivation. Brought up by the brutal Scarrans, who tortured him for his weakness, he learnt to be strong and ruthless. He also learnt to hate the race who created him. He will stop at nothing to prevent the Scarran overthrow of Peacekeeper rule.

The thing he wanted most was Crichton's knowledge of wormhole physics. Unable to extract it from him with the brain-searing Aurora Chair, he implanted a neural clone chip in Crichton�s head.

From that point on, we�ve seen two faces of Scorpius � the ruthless, rational scientist, and the lighter touch of his clone, Harvey. Semi-autonomous, Harvey seems to be on Crichton�s side, living in his mind as another prescence, encouraging him in his wormhole studies. He�s even helped him from time to time by suggesting plans and providing support.

Things have not gone so well with the real Scorpius. When he struck a deal with Crichton, the earthman turned the tables on him. The command carrier he took from Crais after his Gammak base was destroyed was annihilated, and his authority suspended by the pitiless Commandant Grayza.

Key episodes: Nerve, The Hidden Memory, Look at the Princess trilogy, Liars, Guns and Money trilogy, Die Me, Dichotomy, Incubator, Revenging Angel (for Harvey), Into the Lion's Den pts 1 and 2.

Read our actor profile of Wayne Pygram.