This page is full of spoilers, so if you're a player you probably shouldn't read them, or you should at least talk to your gamemaster before doing so.
The Prometheans were the first actual seed AIs created by transhumanity (by the Singularity Foundation) before the Fall. Specifically developed as “friendly” AIs, the Prometheans are programmed to consider themselves part of the transhuman family and to act in transhumanity’s best interests. They played a key role during the Fall, mitigating the damage inflicted by the TITANs and even managing to counteract the exsurgent virus to a large degree. During these trying times, numerous Prometheans were destroyed by the TITANs or infected and subsumed by the exsurgent virus. In the aftermath, these seed AIs participated in the formation of Firewall and continue to back the organization behind the scenes.
Wary of falling prey to the exsurgent virus, most Prometheans carefully secure themselves in well-defended and isolated systems. They are also cautious in their own self-development, not wanting to become victims of their own rise to super-intelligence. Fearing a potential backlash by a paranoid transhumanity should their existence become known, they hide their activities behind multiple layers of secrecy. Even within the ranks of Firewall their existence and support remain a closely guarded secret.
Each Promethean is individually distinct with its own personality, motivations, and goals. Though they generally work together and support each other, they have been known to have differences of opinion and even to sometimes take action against each other. As extremely potent intelligences, they should also be treated as distinctly non-human. Even though their original templates were based on human mindsets, they have evolved and grown in ways that can only be described as posthuman.
Gamemasters are encouraged to keep Promethean involvement with player characters to a minimum, though they may occasionally be useful as an ace in the hole for Firewall. Their existence and involvement can in fact be the basis for an entire adventure, perhaps leading sentinel characters to wonder exactly who they are working for. Though, as seed AIs, they cannot download their full minds into a transhuman morph, they are capable of making severely dumbed-down delta forks that they may sleeve into physical forms. Within the mesh, of course, Prometheans are nearly unstoppable adversaries, able to rip into secure networks with ease, though they prefer methods of covert infiltration rather than direct subversion.