The player, by default named SARA, is the only physical character of the game.
SARA is never actually seen in-game, however it is implied she is a normal-looking human in the Pilot Wave Radio messages.
SARA is shown to have been a Bosonic piloting robot aboard one of the Vanguard's light gunships. At some point before the start of the game, she and her ship were damaged and she was shut down for repairs. Later, the last of the human insurgents hacked her systems and removed her safeguards, turning her into the deadliest pilot ever seen.