The Arcanums are a mysterious and powerful alien species that operate across multiple realities and the cosmos, who are involved in many conflicts across reality pertaining to other alien civilisations, although their motivations are unclear. A group of individuals from this species known as The Elders head these missions and select many different alien species to serve their cause. The G-Man is a most notable member of the species.
The Arcanums appear to be humanoid beings, with two legs and two arms, and most of the time appear exactly like human beings do on earth. However this is the exception of the Elder Supreme, who has light green skin and black retracted eyes, although it is unclear if this is the Arcanums true form. They have the ability to blend in and somewhat change their appearance, although this seems to be rare, as for example The G-Man has only changed his appearance twice, as did his father. A trait they share is that most of the Arcanums are tall and thin, with pale skin and darkened hair and bright blue-green eyes.
They are also smartly dressed, choosing to wear suits and jackets.
The Arcanums (or at least the Elders) have knowledge and the ability to travel through time and space and are even able to change reality, such as stopping time. They are also armed with teleportation devices (which is kept within their briefcase).
Despite being able to take on the perfect disguise of whatever civilisation they are infiltrating, the Arcanums have a slight difficulty blending in. For example when The G-Man took on the form of a human being on earth, he had difficulty in interacting like a human, mostly struggling with his words, although he didn't seem to care. His body language also made it clear that he wasn't human. But overtime G-Man became accustomed to earth life, which made it easier to blend in among the populace, although now and again has certain difficulty.
Most of the Arcanums come across mostly calm and collected, and possess an almost uninterested demeanor when it comes to dealing with certain tasks.
The G-Man is the first known Arcanum to make his presence known on earth, which was sometime prior to the Black Mesa Incident. Having acquired a crystal sample from the dimension Xen, he delivered it to the facility on his employees orders (the Elders), which triggered the resonance cascade, ultimately allowing hostile alien species to travel through from Xen and began invading the facility. G-Man nuked the facility around two days following the event, and the death of the aliens' leader Nihilanth was killed, which drew the attention of a multi-dimensional alien empire known as the Combine to invade and enslave the human race within Seven Hours. Just before the detonation of Black Mesa, G-Man placed Gordon Freeman in stasis, intending to use him as s field agent for the Elders, although he didn't disclose any information about them.
Twenty years into the Combine's reign, G-Man began working with them behind his race's back, although this was more of a double cross. Following the downfall of the Combine forces on earth, G-Man attempted to enslave the human race for himself, but was eventually defeated by Nathan Johnson. Having somehow lost his abilities such as teleportation and reality warping, G-Man was forced to live like a human on earth, and began to go deep undercover to hide from his former employees, who wanted him to answer for what he had done.
The Elders began working with a secret society on earth nicknamed the Clandestine Company, which had plans to takeover the earth. Due to G-Man's absence, the Elders sent their field agent Jim Dewar to oversee the Clandestine Company's activities in City 17, although he was presumably killed in action due to an experiment gone wrong, although the Elders managed to bring him back.
- The G-Man/ Frank Blackstone
- Elder Supreme (deceased)
- "Jim Dewar" (unknown)
- G-Woman/ Louise Ashton
- The G-Man's Mother
- The G-Man's Father
- Beth Blackstone
- Leonard Blackstone
- Chell Blackstone (cross with a human being)
- Sophie Hunt (cross with a human being)
- Wade Blackstone (cross with a human being)
- Grandpa G-Man
- Uncle G-Man