Lucius Fox had been working for Wayne Enterprises for some time before the events of the series, having become the head of the department by the time Bruce Wayne began operating as Batman. Alfred Pennyworth claims that Lucius had been present in Bruce's life before he became the vigilante, having helped raise Bruce in addition to working on his tech.
At some point, he became aware that his boss was the vigilante known as the Batman, having either deduced it himself or been told personally by Bruce. He agreed to help him in his endeavors, hoping to help make the city safer for his children Luke and Tiffany. Lucius designed and supplied the vigilante with many various gadgets and equipment, including the Batsuit, Batcomputer and the Batmobile. Due to his work on many of Bruce's bat-tech, Lucius was unable to spend time with his family, particularly his children.
After his drones were destroyed by Roland Desmond, Lucius created and deployed a new Bat-Drone to help Batman in the field. When contacted by the vigilante, he told him of the new features he had installed and how they might be useful to him in the field. He was later contacted by Batman, who had collected a data chip from a Children of Arkham member's radio, asking him to analyze it and find out how it could listen to the Police Radio. Lucius agreed to and arranged to meet Bruce Wayne the next morning.
When Bruce arrived, Lucius spied on him and Regina Zellerbach as the two discussed a meeting between the board to decide on what should happen to him. They discussed the possibility that Bruce may be forced to loose most of his technical support and access to the Wayne Enterprises R&D, which could knock onto Batman's activities. Lucius also revealed that he had found out how the Children of Arkham gained access to the GCPD's coms throdeugh a backdoor he created in the system to help Batman and prepared a patch for the Batcomputer to make it less susceptible to these compromises. He also provided Bruce with a number of new gadgets he had prepared, including a new cowl with infra-red vision and a new form of sticky bomb. When Bruce left to meet with Regina, Lucius handed a drive containing the patch to him.
After learning that Bruce had been asked to leave Wayne Enterprises, Lucius met up with him to discuss what might happen and whether Wayne Enterprises were aware that they had hired a known criminal and member of the Children of Arkham, Oswald Cobblepot, as their new CEO. Lucius also pondered whether to stay at the company and keep an eye on the R&D department to make sure Cobblepot did not access and use its gadgets for Children of Arkham activities or to leave and work for Bruce, continuing to help Batman in the field. Regardless of the choice Bruce makes, Lucius swore to help Bruce in his endeavors.
Depending on the decision made in the last episode, Lucius will perform the following roles to help Bruce in his war against crime:
If Bruce asked Lucius to stay at Wayne Enterprises, he has been sending reports and tabs on Cobblepot's visits to the R&D department. He is contacted by Bruce after his Bat-Stunner malfunctions in the field and is unable to disable one of the Children of Arkham's new drones. Realizing that he had not kept a close enough eye on Cobblepot, Lucius apologizes to Bruce and looks into the issue, promising to contact him once he has found what has been causing the tech malfunctions.
He later calls to tell him that Cobblepot installed a Black Box on the Wayne Enterprises network and that it would hack the Batcomputer if not dealt with immediately. However, at the same time, Wayne Manor is being seized by Harvey Dent and his enforcers, forcing Batman into a difficult decision. If Batman chooses to go to Wayne Enterprises and stop Cobblepot, Lucius, from a safe place, will guide him through the halls and warn him of any upcoming threats. He also confirms the black box installed and how to destroy it.
If Lucius is asked to leave Wayne Enterprises and work for Bruce, he repairs the Batsuit after it is severely damaged in a fight with Lady Arkham and creates a new device called a Strobe Grenade for him to use in the field. When Bruce returns following an incarceration at Arkham Asylum, Lucius shows concern over his current condition and helps synthesize an antidote to the Arkham Drug. He also gives him the Strobe Grenade before he leaves to investigate the Vale residence.
After one of the Bat-Stunners malfunctions, Lucius helps diagnose the problem, realizing that it is being caused by a receiving single coming from Wayne Enterprises. Suggesting that it may have been better if he stayed at the company, he realizes that Cobblepot had introduced a bug into the network. He helps diagnose the problem, deducing that a Black Box had been installed into the network, and suggests for Batman to destroy it. At the same time, Wayne Manor is being sized by Harvey Dent and his enforcers, forcing him to decide which he wants to protect.
If Batman chooses to stop Cobblepot from hacking his tech, he will ask Lucius to observe his coms and tell him if he sees the Black Box. Upon seeing it in Wayne Enterprises, Lucius will tell him and advise him to destroy it.
However, if Batman decides to stop Dent, Lucius will tell him how it is too late to stop Cobblepot and that his tech will no longer be operational. He watches as the Batcomputer is disconnected from its power supply.
Five days later, one of the prototypes is stolen from Wayne Enterprises by Selina Kyle. Depending on who Batman chose to stop in the last episode, Lucius will either be alerted by Alfred after they notice an alarm at Wayne Enterprises has gone off or contact Bruce after noticing the prototype is missing. After Alfred was kidnapped by the Children of Arkham, Lucius helped track him down and provided him with another suit for him to wear. Depending on who Batman stopped, he will give him either the newly created Mark II (if Penguin's hack was interrupted) or one of the prototypes (if Two-Face's invasion was stopped).
Lucius stayed to help Batman whilst he investigated the Vale residence, communicating with him from the Batcave. He later sent a message to the GCPD informing them of the Children of Arkham's attack on Arkham Asylum. A week after the riots, he sent a bottle of an unspecified beverage to Bruce and Alfred, hoping they would recover from the injuries sustained from that night.
Lucius was called in the early morning by Alfred and Bruce, hoping that he could help them solve the Riddler's puzzle box. Arranging to meet that morning in Wayne Enterprises, Lucius also revealed that Tiffany would be starting her career at the company. Lucius met Bruce in his office, but the two are unable to figure out how to solve the next part of the riddle; a radio wave emitter that could be modulated. During this, Tiffany came into the office to greet them, having slipped out of orientation. She showed interest in the Riddler's puzzle box and offers to help. After she left, Lucius asked Bruce to bring her into the fold and let her help him as Batman. As they went to his office to investigate the puzzle box, they met Agents Avesta and Blake, who wished to speak to Bruce about something.
Lucius continued to investigate the Riddler's puzzle box, he discovered a missile had been fired at Wayne Enterprises. Realizing that it had been set off by the signal, he fired up the emergency evacuation alarms and called Bruce to tell him what had happened. In his final words, he asked Bruce to look after his family and stated how proud he was to have helped Bruce on his crusade. As the missile hit his office, Lucius died instantly in the blast.
Following his death, Bruce swore to defeat the Riddler and make him pay for Lucius' death. His family was also left in mourning, Tiffany in particular wished to have spent more time with him before his death. When she learnt Bruce had been partially responsible for his death, she was furious at him. Lucius' death was also used by the Riddler to mock Batman, having figured out that the vigilante had worked closely with him. This was also learnt by Commissioner James Gordon, who worked closely with the Batman and began to lose trust in the vigilante after learning about this.
Lucius was one of the smartest people at Wayne Enterprises, having created a number of devices used by Batman and designed a number of products used by the company. He was also one of the most honest people Bruce knew, holding no information or secrets from him. Lucius also cared deeply about his children's future, especially with the crime-ridden state that Gotham was in at the moment. Because of this, he worked with and helped Batman.
Whilst he was close with much of his family, Lucius seemed to have the better relationship with Tiffany. The two would work on science projects, including a rocket and drone technology, with Lucius admiring that she was more intelligent that he was. Following her graduation from Cornell, she was hired by Wayne Enterprises' R&D Division, hoping to work with her father. However, her first day was tragically the day he was killed indirectly by the Riddler. After learning Bruce had been partially responsible, she was furious at him for this, though it is unknown what later actions will be caused by learning this information.
Lucius was one of the people in Wayne Enterprises that Bruce trusted with his private life as the vigilante Batman. As well as provide technical support and gadgets, Lucius would support him during the scandal with his parent's ties to Gotham's underworld and after he was forced to leave the company. He also personally designed many of the gadgets used by Batman in the field, including the Batsuit, many of the handheld gadgets and the Batcomputer. Lucius died working on one of the projects Bruce had asked him to, working out a puzzle box left by the Riddler. Following this, Bruce felt responsible for his death and swore to bring his murderer to justice.
Though the level of friendship between them was unclear, it seems Lucius and Alfred were on friendly terms. He also felt sympathy as he watched his brutal treatment at the hands of Lady Arkham and the Children of Arkham.
- Lucius' voice actor, Dave Fennoy, had previously voiced another iteration of Lucius Fox in Batman: Arkham Knight and various criminals in Batman: Arkham Origins. He has also been closely associated with Telltale games before their Batman series, having voiced characters like Lee Everett in the Walking Dead series and Bluebeard in The Wolf Among Us.