Sophia

Sophia was a secretary at Group 935. She was attracted to Maxis, who was also attracted to her.

Original Timeline
Sophia was Doctor Maxis's personal assistant, and was tasked with delivering a letter to the Reichstag High Command before the events of Der Riese. In Call of Duty: Black Ops, it is revealed that she is attracted to Dr. Maxis and that he has started to view her as a distraction because he is attracted to her too. It is also revealed that she created the Monkey Bomb with an actual monkey as the test subject. At some point, Sophia was attacked by subject 2-6 and possibly infected. After the death of subject 2-6 Sophia was called down to Maxis' office for questioning. Maxis sits her down and insists she drink her tea, Maxis asks her to show him her arm, however Sophia refuses. Maxis calms her down and tells Sophia that he would never hurt her. Suddenly Sophia begins to cough and drops her cup where she can be heard falling to the ground and moaning in pain. Maxis reassures Sophia that everything he is about to do is for her own good. Her fate is unknown but she was likely poisoned. Sophia appears in Issue 3 of the zombies comic series, as an AI security system protecting Zero Base. When Marlton Johnson attempts to crack the system, Sophia enables security measures to trap the group. She constantly attempts to thwart the four "intruders" by leading the zombie horde toward them, and setting death traps for Marlton. Eventually Marlton reaches the primary control room, where he presumably disables Sophia by using an axe to destroy the system.

Alternate Timeline
Like the Original timeline, Sophia was presumably infected by subject 2-6. In order to save her life, Maxis was forced to convert Sophia into the Strategic Operations Planning Heuristic Intelligence Analyzer, or S.O.P.H.I.A for short. In Gorod Krovi, the characters are instructed by S.O.P.H.I.A. to perform various tasks to initiate Ascension Protocol so they can receive a power core in return to repair Nikolai's mech suit. These tasks include retrieving Gersh for her to extract information from him, escorting a malfuctioning Russian Mangler and Valkyrie Drone for her to analyze, retrieving information from a fallen Groph module, terminating a self destruct sequence, and downloading information on interdimensional travel. Once the tasks are finished and Ascension protocol is complete S.O.P.H.I.A dislodges from her normal position and departs the map in search of Maxis. In Revelations, she scarifices herself along with Maxis to destroy the Summoning Key and save the universe.

Trivia

 * She is apparently disliked by Samantha, as she remarks "First I'll find Teddy, then Sophia" when acquiring the L96A1 from the Mystery Box.
 * Her zombified corpse can be found in Revelations.