- "The pre-Socratic philosopher Thales of Miletus, known as the father of science, believed that for any event there was a natural cause, even if we couldn't see it... and he thought that with perfect knowledge, man could control anything.. everything."
- —Cayden James [src]
Cayden James is the leader of Helix, an organization uniting masterful hacktivists. Although no official case was formed against him, he was denoted as a "person of interest" by A.R.G.U.S. and illegally imprisoned in a black site facility. Cayden's Helix allies, led by Alena, eventually rescued him with the help from Felicity Smoak. His time in custody caused him to go insane, and he developed a plan to wipe out the world's Internet, recruiting Black Siren to his side and clashing with his former allies Alena and Felicity, as well as Team Arrow.
Founding Helix and A.R.G.U.S. imprisonment
At some point Cayden founded Helix, an organization uniting hackers that pursued political activism. Considered by A.R.G.U.S. to be 20 times more dangerous than Snowden as a security risk, Cayden was captured by the organization when he was supposedly trying to hack an A.R.G.U.S. transponder. Athough his crime was not proven in court, Amanda Waller illegally gave the order to keep him imprisoned as a "person of interest". Cayden was moved to a black site prison, which was eventually located by his Helix allies in 2017.
The Helix rescue team led by Alena and Felicity Smoak ventured into the facility, opposed by A.R.G.U.S. security force and Team Arrow. They successfully extracted Cayden and moved him to an undisclosed location. Back in the command of his organization, the Helix leader decided to cut off ties with Felicity, considering her ties to Team Arrow a liability, but worked with the code to figure out a program she was looking for that would allow to locate Prometheus's location. Leaving a flash drive for Felicity's use, Helix evacuated from their old base to a new location.
According to Alena, Cayden was greatly changed by his time in prison. He developed a plan to destroy the world's Internet as whole, even worse than the Calculator's plan. Seeking out allies for his scheme, he observed the battle on Lian Yu and saved the life of Laurel Lance/Black Siren, adding her group's strength to the power of Helix.
When Alena disagreed with Cayden's plans, he attacked her, making the young hacktivist escape Helix while pinging his phone in Corto Maltese. Alena looked out for Felicity's help, and the two tried to contact Amnesiac for the ghost drive. They eventually came to the old Helix building intending to prevent Cayden's plans, but were captured by his team, which included the infamous Black Siren. Cayden explained his disappointment in Alena being duped by his Corto Maltese phone and tried to execute the two women, but was stopped by Team Arrow.
Cayden and Black Siren's group went on their path to the International Domain Name Directory vault, slaying all the guards. They were pursued by Team Arrow, with Oliver Queen taking on the role of Overwatch. Thanks to her personal presence on the field, Felicity Smoak managed to remove Cayden's Internet-threatening virus, but only through taking down the facility's firewall processors, with them exponentially overclocking and the cooling system disabled. However, it was never Cayden James's plan to take down the Internet, but rather to get Felicity to take down the firewall, leaving her "digital fingerprints". Once Felicity had taken down the firewall, Cayden was able to upload a critical piece of code to Arclight. As such, he would be able to frame Felicity for the results of his true plan.
With Black Siren's help, Cayden created a new plan, involving a terrorist attack on Billy Joel's concert, masking his men as police officers. As Oliver Queen arrived at the scene of the crime, he was confronted by Cayden, who explained that the bomb was a hoax and he merely wanted to see Oliver and talk with him tête-à-tête, saying that Oliver was responsible for the death of his son, and all Cayden truly seeks is revenge. He enacted a part of his revenge by releasing footage of Team Arrow members beating up his goons masked as police officers, swaying public opinion against vigilantes, who were seen "attacking SCPD officers".
Cayden was once close with Alena, who became immediately distraught and very concerned for Cayden as soon as the Helix team found him, losing her cool. He is also a very suspicious individual, ordering Alena and Helix to cut ties with Felicity altogether after being saved, not trusting an individual affiliated with Team Arrow. Cayden is also self-righteous, physically harming Alena for daring to question his plans for the world that would threaten the lives of millions. He possesses a calm, collected, yet also smug attitude, considering everyone a pawn in his plans. Ultimately, however, he is motivated by passion for his dead son, whom Cayden considers a victim of Oliver Queen's activities as a vigilante.
- Computer specialist/Master computer hacker: Cayden is a highly skilled computer hacker, so much that he was able to hack an A.R.G.U.S. transponder. His abilities made him a "person of interest" for A.R.G.U.S. and a security risk considered 20 times more dangerous than Snowden. As soon as he was freed from captivity, he managed to immediately figure out the code for the program that Felicity needed, but neither she nor Alena could figure out on their own. According to Alena, he is the best hacker on Earth One so far that no one has ever heard of him. His skills surpassed those even of Felicity Smoak's hence making him one of the best hackers and one of the most intelligent individuals in the multiverse.
- Genius-level intellect/Master tactician/Leader: Cayden not only created and ran Helix as a powerful organization, but also inspired loyalty into hackers under his cause, so much that they staged a massively dangerous operation to rescue him from a heavily guarded government facility.
- Prototype T-Sphere: Cayden used the Prototype T-Sphere that Black Siren stole from the Arrowcave against Oliver Queen (under the guise of Green Arrow). 
- Cayden James is similar to past characters Michael Emerson has played such as Benjamin Linus from Lost and Harold Finch from Person of Interest.
- He is similar to Harold Finch in that: they both address people by Mr/Ms, they do not enjoy killing, they both have genius level intellect, they were both noted to be a "Person of Interest" which Michael Emerson had a co-lead role in, they are both excellent hackers.
- He is similar to Benjamin Linus in that: they are both leaders of their organizations, they are both villainous.