Carbon

Carbon, known as Decoy (デコイ) in Japan, is how the System refers to the artificially created humans that live on Terra (Earth). They were also referred to as Betas (Decoys in Japan) by the Master of Elysium.

Characteristics
Carbons are essentially "artificial humans" created with their own language and culture, and the question of what they are and what their purpose is is a major theme to series' elements of mystery. Like normal humans, they are organic beings made of flesh, but are able to replace their regular body parts with mechanical implants, ranging from simple arm replacements to full-body overhauls. Despite this, Carbons are at least partially if not entirely robotic. Many Carbons have mechanical portions of their bodies, some as simple as replacement parts and "patches" while notable others like Teisel Bonne and Glyde have almost entirely mechanical looking bodies. While MegaMan Volnutt is not a Carbon, he is considered a human like all Carbons, being unknown if his current body has any difference from Carbons. Curiously, it seems exceptionally rare for female Carbons to have any mechanical parts, suggesting that it may be considered unattractive. (Early character designs for Mega Man Legends show a nurse with a buster-like syringe on her arm. )

Aside from similar biological actions, Carbons also behave more or less like humans. They are prone to building up societies, and have distinct cultures and beliefs varying by location. Carbons seem more or less ignorant of the ancients who came before them, and in many cases revere them as myth. They also make use of technology left behind by the ancients that is retrieved by Diggers in ruins.

Reinitialization
A recurring theme in the Mega Man Legends series involves awakened ancients attempting to "reinitialize" Carbons, i.e. wipe them out en masse. When MegaMan Juno is awakened, he explains that it's his job to routinely reinitialize Kattelox Island to keep the Carbons living on it from overpopulating. In Mega Man Legends 2, Sera planned to wipe all Carbons and restore the population from Elysium.