Reg is a robot who appears to be a little boy. His actual age, origins and even name are unknown since he can't recall anything about his life before his encounter with Riko. He was named Reg by Riko after a dog she used to have.
Having an artificial body, Reg might be the only being completely immune to the Curse of the Abyss, because of that he is sometimes referred to as "The Treasure of the Deep."
According to ???, Reg could be an "Interference Unit" of one of the lower layers.
Reg has tan skin and dark hair. He wears a metal helmet with two asymmetrical horns protruding out of the sides and what appears to be a glass lens in the front, which occasionally will glow with a strange symbol shared by all artifacts. Underneath his helmet is what looks similar to a jagged metal headband of some sort, with bolts on either side keeping it in place on his head. His ears are slightly pointed. Reg's eyes are yellow and his pupils are vertical slits, like a cat. There are two red patches of skin on his cheeks, and four more on either side of his ribcage. His eyebrows are small and gray. Though he is a robot, the only parts of him that appear to be mechanical are his arms and legs, which are bulky compared to the rest of him. He has nipples, a bellybutton, and even human genitals.
He is usually shirtless, save for the tattered red cape he was wearing when Riko found him. His pants are a washed out green and purple, are baggy, and stop just below his knees.
Despite being a formidable fighter, Reg is rather shy, naive, and unassertive. He blushes easily and often cries when in distress. However, when forced into danger or an unpleasant situation, he is shown to be hot-tempered and sharp, compared to Riko's analytic, noncombatant role. Regardless of his skittishness, Reg has made it his sworn duty to protect Riko, and doesn't hesitate to put up a fight when she is in harm's way.
History EditVery little is known of Reg's past, as he has none of his memories from prior to meeting Riko. He was found by Riko in the Abode of Fossils at a depth of 100-220 meters after Reg uses his incinerator to save Riko.
He presumes he is from the bottom of the abyss, as a sketch from Lyza shows a likeness to him. According to her notes, she first encountered him around the 7th layer. He had at one point before met Ozen the Unmovable, as well as supposedly been close to Faputa, though he doesn't remember any of this. As he descends further into the abyss, Reg's memories are coming back in little bits at a time. He eventually recalls that at some point he had journeyed alongside Riko's mother, though he does not remember any specific details. According to Faputa, Reg's name was Reg even before he lost his memory.
The incinerator is Reg's version of Sparagmos, the Origin-Guiding Light. An object in its path disappears, "as if it comes undone... Shortly afterwards, the surrounding air ignites to nothing." The incinerator is also capable of "tensing up" the force field of the Abyss in an undefined manner. The size of the beam changes depending on Reg's will . It is important to note that the Incinerator does not just burn objects, it is connected to the Abyss in an unknown way. The name implies that everything hit by the light returns to the Abyss; for instance when Reg kills Mitty he makes a comment about Mitty's soul "cycling again." Nanachi also comments that Reg's incinerator "has the power to rewrite the rules of the Abyss".
The incinerator is a relic that is part of Reg. All relics in the Abyss contain a pattern that signify the number of uses left before becoming useless. Along with passing out for 2 hours after 10 minutes of using the Incinerator, the pattern in Reg's helmet decreases, . Electricity seems to recharge it, as the symbol grew again after Reg was exposed to electricity at Idofront.
It could also be possible that when over used and he runs out of energy he loses his memory. This is possible why Riko was able to wake him up with a jolt of electricity.
Reg's arms can extend up to 40 meters each. He can shoot them to the top of cliffs or grab things very far away. The cord attaching them is very durable. Using these arms does not reduce the pattern on Reg's helmet because they require a minimal amount of energy.
Reg's senses of smell and hearing are stronger than that of a human's. Nanachi has commented to themself that he reminds them of a dog by the way he follows his nose. He feels simulated pain.
As commented on by several characters, Reg's body is extremely durable, even to the point that Ozen the Unmovable couldn't break him even when slamming him into the floor with all her strength. Despite his high durability, Reg is agile and weighs little. His wounds heal at a faster rate than a human's, and he has a very high pain tolerance. His navel is the thinnest part of his skin, making it a weak spot.
- Reg is often associated with dogs. He is named after a dog Riko had when she was younger, and is also sometimes compared to a dog, even by those who aren't aware of the origin of his name.
- He recognized Nat hidden under cloak, and is able to tell that Marulk is a boy. How he did this is unknown.
- He is slightly disappointed that his muscles won't grow.
- He is able to get erections, despite being a robot.
- Akihito stated in an interview that Reg was inspired by a Cave Story character named Quote.