Tom Cox is a deformed renegade who later worked for the Styx in the Tunnels series. He is a former Colonist who was banished to the Deeps of the Earth for the rest of his life. He became hideous inside and out, due to the hard life of surviving in that harsh land.
Cox later found work for the Styx, and he was given the job of trying to track down Drake and Will Burrows. He actually did get to torture Will in Closer. In Freefall, he was almost like an assistant to the Old Styx, the leader of the Styx.
Tom Cox first appeared when he retuned a rock to Drake, who was teaching Will and Chester how to shoot. Will is repulsed by the man's ugly face and sneaky manner of talking. Cox leaves Drake alone because the two have a truce. Drake later explains to the boys that Cox is an example of a bad renegade who will take advantage of you if you are not careful.
Cox is later seen by Will and Elliott, who came upon a Styx interrogation. He is seen working with the Styx, who are torturing a man on a stake. The two teens think it is Drake, and Elliott has Will shoot him to put him out of his misery. It turns out this was not Drake- the Styx set the whole thing up using a trapper renegade.
Cox is at the Pore with the Old Styx, who is investigating the event when the Rebecca twins were pushed into the Pore. Cox offers his condolences and says there is a story when a Colonist fell into the Pore and eventually made it out. The Old Styx laughs at this.
Cox meets up with the Old Styx at the Styx Bunker, which has been destroyed by Drake. A Limiter soldier says that the remaining Dominion Virus there was denatured by Drake's bombs. Cox agrees with the Old Styx that Drake must be killed.
Cox later appears at the Pore with the Old Styx again. Limiters are now parachuting into the Pore with gear, after learning that the Rebeccas are still alive down there. Cox is happy about this, but the Old Styx adds on that Elliott and Will Burrows are alive, and Drake is loose on the surface, trying to fight the Styx. The Old Styx then says their deal is up, and has 2 soldiers throw a shocked Cox into the Pore.
Cox survived the fall into the Pore and later met up with the Rebeccas in the Garden of the Second Sun (the Earth's inner world). He was caught by New Germanian officers after stealing food from the city. The Rebeccas are surprised to see Cox all the way down here at the center of the Earth. He claims to have followed the Limiters; the twins see through this. A reluctant New Germanian colonel agrees to take Cox with them as they search the jungles for Will and his family.
When Will and Dr. Burrows are caught by the Styx on top of a pyramid, the Styx surround the top. Cox tortures Will, who has been stripped shirtless and tied up. The Rebeccas want to make a deal where Elliott gives the Dominion Virus phials back. The Rebeccas begin a loudspeaker countdown, so every minute where Elliott fails to appear, Cox will cut off a finger from Will. Elliott is watching this from a tree, and cannot bear to see Will tortured like this. Elliott then shoots Cox in the head, causing him to die a gruesome death as his head explodes like a melon from all the tumors he had.
The Rebeccas kill Dr. Burrows in retaliation for Cox's death. Later on, the Rebeccas joke of building a statue of Cox in New Germania to honor him, and also give him a state funeral.
- In many ways, Tom Cox is like Jango Fett from Star Wars. Both of them are bounty hunters/renegades who end up working for the main villains (Sith/Styx). They are both sneaky and evil, and go after the main characters. They also both end up dying from head injuries (Jango gets decapitated, Tom gets shot in the head).