The golden age story tells of Aarkus (who was called the Vision before the Synthezoid who was created by Ultron who took the same name) being brought to earth by a scientist named Enoch Mason who found that smoke is the gateway to the supernatural world with his Dimensional Smasher. Mason called fourth Aarkus (and was later revealed to be the keeper of law in a place called Smoke World, a other plane of reality where law and order are absolute) Aarkus' first adventure found him defending Dr. Mason and his Daughter from Brains Borelli, a mobster who funded Enoch's experiments and wasn't paid back. It was stated that Aarkus could only be seen in his true form by a person who is about to die. but to activate his true form he also needs to be exposed to a source of smoke: this could be anything from cigarette smoke to engine exhaust.
Aarkus was created by Jack Kirby and Joe Simon and first appeared (as Vision) in Marvel Mystery Comics issue 13 (1940). It is very likely that Aarkus has inspired the character also named the Vision some years later, whom became a member of the Avengers. Stan Lee, through he didn't create Aarkus, wrote multiple mid-issue paragraphs outside of the main plot in character that explained his motivations, how his planet worked, and how he kept the peace, and it was rumored that Lee wanted him on the Avengers and created the android Vision to compensate.
Mayor Story Arcs
Retelling of Origin
It was later revealed that Aarkus and his people came to Earth-616 from another dimension to answer their true calling in life, which was to help Cosmic Cubes all over the Universe gain sentience. Aarkus was assigned to be the caretaker and a midwife of sorts to the Cosmic Cubes of Earth. Aarkus became distracted from his mission when World War II broke out, which he fought in as both a member of The Axis and The Allies. After the War, Aarkus mostly retired from his active duties and mostly spent his time on his home world, through he would also return to Earth at times to still stop crime.
Corrupted by D'Spayre
Sometime later; Aarkus was assigned to protect a Cube, that unbeknownst to him, was being corrupted by Humanity's fear and despair. The Cube's corrupting powers began to have a dramatic effect on Aarkus and in the end he was overwhelmed by the demonic being called D'Spayre.
Return As Aarkus
When The Invaders were brought to the year 2008 by a Cosmic Cube, but apparently not the one that was corrupting Aarkus, Doctor Strange, The New Avengers, Paul Anselm and a few of The Invaders found Aarkus hiding with his Cube in an ancient sewer. With Echo‘s help, Doctor Strange took the Cosmic Cube from Aarkus, purified it and then used its power to banish D'Spayre from existence and by doing so restored Aarkus to his true form. He recently helped reunite the original members of the Invaders and assisted them on their travels.
Aarkus, The Aetheric
According to the mutant known as Legion, Aarkus would grow deeply paranoid of the presence of mutants after reading lots of anti-mutant material: because his species seen many things in a black or white manner, Aarkus would take the propaganda completely literally and started to organise for a mass murder of mutants: this would result in the destruction of the X-Men after they tried to stop him and were completely overwhelmed by his collection of smoke generated weapons. After seeing this vision, Legion considered killing Aarkus but he'd eventually opt to talk him out of his scheme, calming him down and getting him to stop his genocidal crusade before it even started.
Powers & Abilities
Aarkus's main ability was being able to manipulate smoke in multiple different forms: he could move within sources of smoke created (seen by him as dozens of doors leading all over the universe) as well as being able to vanish into smoke. He could also get stronger from vapor around him and could focus mist into solid chunks hard enough to smash through solid steel rather easily. He could also create dangerous weapons from smoke and could choke people to death by shifting into smoke and entering their bodies, through as he was very moralistic he wouldn't do this to many criminals, only opting to kill murderers or Nazis by his hand.
Aarkus also had other less showcased abilities. These included being able to freeze people to death with just a touch of his hand, being able to generate frost from nowhere. He could also use what seemed to be a form of telepathy, through he mostly used it to project images or illusions into the minds of his targets, scaring them.
In terms of physical stats, he was almost indestructible: buildings falling on him or even being caught in the ground zero of a major industrial explosion had little effect on him, bullets would harmlessly pass through his body, and punches would barely have any effect on him. He could move faster than the eye could see, even being able to dodge bullets at point-blank range or a full on shotgun blast. He could hit hard enough to break through chains, ragdoll people with one hand, and he could jump high enough to reach a rooftop in a single bound.
Through Aarkus was a alien, he had full knowledge of the English language, and was a capable detective, finding clues and suspects with his powers of deduction. As a guardian of Cosmic Cubes, he had a innate knowledge of how they functioned, where to find them, as well as how to look after them.
While all of this is true, he does have major weaknesses: being removed from a source of smoke for a extended period of time would weaken him, he could still be knocked out by particularly strong poisons in the air (but he wouldn't die) and his alien mentality meant that he could be tricked or misdirected by strong corruptive sources, like magic (in terms of D'Spayre) or simply overwhelming propaganda. This makes him a unpredictable person and one that has had a habit of switching sides out of the blue.