The Millipede is a huge and powerful creature that lurks the Underground below Kazakh City, which has been mutated due to its continous ingestion of the chemical substances discarded from Kazakh's Research Facility. The mutant is actually a multi-organism consisiting of several Severnsi crabs joined together to form its body. Having an unusually aggressive and vicious nature, the Millipede doesn't allow anyone to enter its territory and periodically hunts down the inhabitants of the Underground to feed on them. Having produced extensive damage to the refugees in the Underground, the creature has become known among them as the "Monster of the Underground World" (地下世界の怪物).
Hiryu is asked by the Black Marketer, the guardian of the Refugee Camp, to take care of this creature for their sake, in exchange of the information he needs to open the sealed doors of Meio's Tower. Hiryu agrees to this, faces the humongous monster and succesfully kills it afterwards. A fire-based subspecies known as the Magmapede also exists, which Hiryu faces later on his journey.
Another Millipede can also be seen in a large container in the walls of the Research Facility, probably as an object of study.
The Millipede is a fast adversary, able to quickly burrow and move through the earth, attacking from either the ground or the ceiling with great force. It has several means of attacks, including generating corrosive acid from its body and releasing it in blobs or by turning into a spinning wheel and crashing into Hiryu with its spikes extended. As its body is made up of several Severnsi crabs, the creature can make use of them by expelling and sending them to attack its victims.
While strong and fast, it has a tendency to leave itself open to attacks, usually by standing in place unprotected or by crashing into walls after doing its "spinning wheel" attack, falling on its back and remaining vulnerable until it can straighten itself and escape.
- Ground Assault: After burrowing into the ground, the Millipede springs out with great force, hitting Hiryu if he's close to its location. A small cloud of dust indicates from where it will spring, while a descending shockwave and falling debris indicates its about to appear from above. The Millipede can either stay in the ground/ceiling for a while and perform other attacks, or fly straight across from one surface to the other.
- Lunge: At any moment while it stands still after coming out of the ground or ceiling, the Millipede can lunge forward at Hiryu and attempt to strike him.
- Acid Spit: While hanging from the ceiling, the Millipede shakes its body and releases several globs of acid, covering the entire area.
- Acid Rain: While on the ground, the Millipede starts shooting several globs of acid from its head upwards, which then rain down all around the area.
- Roar: The Millipede lunges back, then forward and produces a strong roar that pushes Hiryu back. The lunge itself can hurt Hiryu.
- Spinning Wheel: The Millipede curls up into a wheel and starts rolling toward Hiryu with its spikes spread outwards. The Millipede either does it in a straight line or by bouncing around as it follows Hiryu. After a while, it crashes into either wall and falls on its back, leaving itself exposed to attacks for a moment before it stands back up and escapes.
- Sewer Crab Summon: The Millipede shakes up and sends four Severnsi into the area to attack Hiryu.
"Archispirostreptus Gigas" is the scientific name of the giant African millipede, one of the largest species of millipede.
The Millipede had several attacks and abilities that never left the concept phase, among them it could grab Hiryu with a long "tongue" and throw him into its spiked back, bifurcate its head into two sides which could either attack individually or form a massive set of jaws, and shoot spikes from all over its body. The concept art also shows a scenario of Hiryu striking it with a Down Strike and the creature splitting into segments and having to re-assemble itself.