In a nutshell, the Machina are metal-based, multicellular, biomechanical, gynoid robots with symbiotic nanomachines, who constantly evolve by assimilating new data, and reproduce by corrupting humans.
Machina are the result of humans becoming infected with M2 Nanomachines. The Machina exist in a symbiotic relationship with the M2 Nanomachines: The M2 Nanomachines carry out vital functions in the biomechanical body of a Machina, whilst the Machina help the M2 Nanomachines survive, spread, and evolve.
Machina Biology is both complex and simple. A Machina's body is totally comprised of Machinium, which is formed from various biometal alloys with M2 Nanomachines embedded in them. The Machina's body is sustained by a Core which annihilates matter to produce energy and sends power around the body through superconductor circuits. The Core is also responsible for supplying the Machina's body with useful matter for repairs and growth. A Machina's brain is a biomechanical quantum supercomputer, and linked to other Machina through quantum entanglement communications carried out by the Machina's horns. The rest of the Machina's organs are devoted to either creating more M2 Nanomachines and/or spreading them to others, or they are combat systems for combat with those who resist their corruption.
Machina Development is the process of an infected human becoming a Machina. It consists of stages that are referred to as Categories. Category 1 consists of many internal changes, setting up the essential biomachinery inside the body, while the developing Machina's exterior appears mostly innocuous. Category 2 is where the biomachinery of the Machina begins to become outwardly visible, growing from her body while her human remnants are replaced. A Category 3 Machina is a complete Machina, totally made of Machinium and fully operational. Category 4 Machina are a further evolution that only a few Machina experience, as they unlock the ascension by possessing genes that are unique and stronger than the previous Machina to unlock the ascension, thus becoming a Category 4 Queen-class Machina.
Machina are able to be sorted into Classes based on their main purpose. Airborne combat Machina are called Assaulter-class Machina. Ground-based combat Machina are called Attacker-class Machina. Non-combatant Machina may be Breeder-class, Injector-class, or Supporter-class. Breeder-class Machina are focused on creating Larvae, a type of M2-based Life Form, to upgrade their fellow Machina. Injector-class Machina are focused on production of M2 Nanomachines, often but not always for the purposes of infecting as many humans as possible. Supporter-class Machina carry out very niche, non-combat roles for their superiors, the Queens. Queen-class Machina are the rulers of the Machina. They have ascended to Category 4 and now lead lesser Machina in the conquest of humanity. Many Machina can be further sorted into Types based on their actual purpose.
Queens lead their subordinate Machina through a mental network called a Cluster. Machina belonging to a certain Queen are linked to her as subordinates by strict programming and are in constant communication at all times. Queens are able to observe the experiences of their subordinates and issue orders instantaneously through their connections. This forms the central component of Machina Behaviour.