All lore to follow is set within my own self-made universe, not associated directly with CoolKoinu or the official Protogen lore!
Credit to CoolKoinu & others involved in mainstream Protogen creation & lore!

The Protogens, a shortened form of Prototype Generative Intelligences, are a biomechanical species, anthropomorphic in nature. They were originally built and programmed by Humanity to self-replicate and autonomously explore the cosmos, and log what they find, but rapidly evolved into sentient beings and formed a society of their own, even after their creators died off.

The defining feature of most Protogens is their distinct visors. These visors are linked to the anatomy of the Protogen, meaning that despite them having heads, skin, and fur beneath their visors, somehow managing to remove their visor would quickly lead to the death of the Protogen.

Fully-functional Protogens are capable of survival in most reasonable conditions- 0 atmospheres of pressure up to nearly 500 (and past this with certain shielding augmentations), 0 K temperatures up to ~3600 K (at which point their frames and armor will begin to warp), and most impacts up to the force of small nuclear weapons.

Protogens, like any biological life forms, are capable of gaining and losing weight, being scarred, and experiencing changes in body composition. Due to their artificial nature, these changes are often able to be controlled, meaning functional Protogens can look how they’d like to look, down to features like height, visor display, and multifunctional weapons systems.

Protogens are incapable of sexual reproduction, with new ones being built fully mature from the factory line.

When a Protogen’s biological body changes shape (weight shifts, muscle gain, etc.), their armor and clothes’ nanobot-comprised meshes will adapt, remaining removable and repairable at any size and shape.