|Family||Kevin Fawkes (brother)|
|First appearance||"Pilot, Part 1"|
|Last appearance||"The New Stuff"|
Darien is described as having an "above-average intellect", and capable of being very deceptive. After their father left them, (it is later learned that their father was a sniper for the government and after his cover was blown, he left his family in order to protect them,) and their mother died, brothers Kevin and Darien were taken in by their aunt and uncle on a farm. While Kevin followed in their uncle's footsteps and played with test-tubes, Darien followed in what he thought to be his father's footsteps and played with locks and was stealing since at least his teens. After being caught because he stopped to give CPR to a heart-attack victim, under California's three strikes law he was sentenced to life in prison without parole. This was where his older brother, Kevin, stepped in. Kevin was a research scientist who had been working on a top-secret project, and cut a deal with the government to get Darien a pardon in exchange for using him as a test subject. Darien would have an artificial gland implanted into his brain which would secret a substance called quicksilver out of his pores covering his body. When his body was entirely covered it would render him invisible. When the testing was over Kevin would remove the gland and Darien would receive the pardon. The operation was successful and after several weeks of testing Darien became quite adept at using the gland even going so far as to turn objects invisible, something that Kevin stated was impossible.
Several weeks into testing Darien started displaying unexpected symptoms. He started experiencing short but severe incidents of pain in his head. Once the pain subsided his eyes would become bloodshot and began to start developing psychopathic behavior such as inflicting pain and attempting rape. One of the team of scientists by the name of Arnaud DeFöhn “quickly” came up with a counteragent to restore Darien’s sanity. While Kevin is grateful for Arnaud’s counteragent, Darien is suspicious of him. As it turns out Arnaud is a terrorist who wants the quicksilver gland for himself. He wants to reproduce the gland and sell them on the black market. He sabotaged the gland before it was implanted into Darien to leak quicksilver into the brain, leading to a breakdown of higher cortical function, initially leading to a lack of inhibition, psychopathic behavior and eventually death. This is called quicksilver madness. He was going to use this to control those he sold it to and would sell the counteragent to keep them in line and have them continuously dependent on him. When Arnaud had his men storm the facility the data was destroyed and Kevin was killed in the assault while protecting Darien. Darien escaped but Kevin was the only one who knew how to remove the gland without killing Darien in the process. Darien is then contacted by a clandestine government organization known only as the Agency who were also the ones funding Kevin’s project. Though Kevin’s data is lost, they were able to recover the formula for the counteragent on Arnaud’s database at his compound.
In exchange for the counteragent he needed to stay sane, Darien agreed, albeit reluctantly, to work as a field agent under their employment. Upon working with The Agency, Darien develops an affinity for his co-workers and opts to continue working there even after his dependency on counteragent was reversed by the Keeper. Over the next couple of years Darien discovers that his body is building up an immunity to the counteragent. The effects of the counteragent would not last as long as in the past and he would fall into quicksilver madness on a more regular basis. He was able to capture Arnaud who confessed that he had a way of reversing the sabotage he did to the gland. Using gene therapy a designer gene is inserted into the gland which kills the toxic producing cells which cures him of quicksilver madness and free Darien from the counteragent and the Agency’s control. This effectively resets the quicksilver gland back to the way Kevin designed it and Darien can be invisible as often as he wants without any danger of falling into quicksilver madness. Now free of the Agency, he elects to stay with them on condition that they continue to find a way to safely remove the gland from his brain.
He has high morals for a career criminal – he could have easily escaped after his final break-in except he surprised the elderly owner into a heart attack, and stayed behind to perform CPR (unfortunately, the officers who caught him and the elderly man himself thought he was molesting the latter). He is a highly talented thief with expert-level breaking and entering skills, learned from his many incarcerations, and finds these skills quite useful in his new career as an espionage agent. His trademark expression is "Oh, crap.", usually said when he realizes he just got himself in trouble.
In the season two premier Legends Fawkes, Hobbs and the Keeper encounter Bigfoot. They discover that Bigfoot has a natural defense to turn invisible and that is the reason why it is so hard to find in the wild. Darien theorizes that a dead bigfoot was found by some rangers and it ended up being studied by the government which Kevin based his gland on. The team encounters the Bigfoot several times and Darien is evening licked by the creature at one point. The Keeper believes that Bigfoot wants to mate with Darien. She explains that the chromosomal make up is XX which means that while Darien is male the gland is female and giving off pheromones which is attracting the Bigfoot. When the team returns and submit their report The Official covers it up. The Official accuses Darien of disrespecting Kevin's memory by claiming that he copied the gland from a 10 ft tall Wendigo instead of using his own genius and inspiration. Darien replies that they never said how tall the creature was.
On one occasion, Darien was briefly possessed by the personality of Simon Cole, the previous owner of the gland, after Cole's residual RNA took over his body thanks to the imprint of his personality left in the gland, causing Darien to see Cole when he turned his eyes invisible and briefly act as him.