Very little has been revealed about the past of the mysterious being who calls himself Interloper. He is one of the Eternals of Earth, although for unknown reasons, he has chosen to have little to do with them or with the rest of humanity. However, he is known to be friends with the Eternal known as the Forgotten One.
Interloper has many times fought the evil cosmic being known as the Dragon of the Moon. His first battles with the Dragon were off the planet Earth, alongside his fellow Eternals. Apparently these battles were on Saturn's moon Titan, and Interloper fought alongside the Eternals of Titan. Later Interloper alone fought the Dragon on Earth. Interloper's final battle with the Dragon before recent times took place in the Sixth Century A.D. on Earth. The Dragon had allied itself with Mordred, leader of the forces at war with King Arthur of Camelot. During the final battle between Arthur's forces and Mordred's, Interloper and his allies (whose names have not been revealed, although Arthur himself somehow played a part) succeeded in somehow imprisoning the Dragon somewhere in space. It seems that Interloper incorrectly believed they had destroyed the Dragon, Arthur and Mordred mortally wounded each other during this battle, and both died. Interloper apparently lived the life of a hermit over the following centuries, having little to do with others. Using his psychic powers, the man named Manslaughter discovered Interloper in the wilderness where the latter lived. Impressed that Manslaughter could find him, Interloper trained him in developing his psychic powers. However, aware of Manslaughter's mental instability, Interloper was careful not to teach him too much.
Meeting the Defenders
More recently, the Dragon placed a woman named Moondragon totally under its psychic influence. Sensing the Dragon's presence, Interloper left the Siberian wilderness and tracked the Dragon to the headquarters of the Defenders, a team of superhuman adventurers, in Colorado. There Interloper joined Manslaughter and the Defenders in doing battle with the Dragon and Moondragon. Moondragon cast the soul of Isaac Christians out from the body of the Gargoyle, one of the Defenders, and the Dragon took control of the Gargoyle's demonic body. Finally, Interloper decided to project his own Eternal life force against the Dragon in an attempt to destroy the creature. Brunnhilda the Valkyrie decided to sacrifice her life force as well. Needing mortal vessels in order that their power might defeat Moondragon as well, Interloper and the Valkyrie asked Manslaughter and the Defender Andromeda to add their life forces as well. The two agreed, and joining hands, the four allies formed the "Dragon's Circle" and hurled tremendous power at the Dragon, Moondragon, and the Gargoyle. The rest of the Defenders went to rescue endangered innocents, and when they returned, Interloper, the Valkyrie, Andromeda, Manslaughter, Moondragon, and the Gargoyle had all seemingly been transformed into statues of ashes and dust, and the Dragon of the Moon was apparently gone. With some members of the "Dragon's Circle" returning it is unknown whether they all will return from where ever they are.
Immortality: Like all Eternals, his life force is augmented by cosmic energy and he has total mental control over his physical form and bodily processes even when he is asleep or unconscious. He is functionally immortal in the sense that he is immune to the effects of aging and is immune to all known Earthly diseases. However, this does not mean that Interloper is incapable of dying.
- Superhuman Strength: Interloper possesses superhuman strength that is much greater than that possessed by the average Eternal. He can lift up to 40 tons without making use of his other powers to supplement his physical strength.
- Superhuman Speed: Despite his great size and girth, Interloper can run and move at speeds greater than even the finest human athlete.
- Superhuman Stamina: Interloper's highly advanced musculature generates considerably less fatigue toxins during physical activity. He can physically exert himself at peak capacity for several days before fatigue begins to affect him. Much like his strength, his physical stamina is considerably above average for an Eternal.
- Superhuman Agility: Despite his size, Interloper's agility, balance, and bodily coordination are enhanced to levels that are beyond the natural physical limits of even the finest human athlete.
- Superhuman Reflexes: His reflexes are similarly enhanced and are superior to those of the finest human athlete.
- Superhuman Durability: Like that of all Eternals, his life force is augmented by cosmic energy and he has total mental control over his physical form and bodily processes even when he is asleep or unconscious. As a result, he is highly resistant to physical injury. Interloper can withstand high caliber bullts, great impact forces, exposure to extremes in temperature and pressure, and powerful energy blasts without sustaining injury.
- Regenerative Healing Factor: Despite his great resistance to injury, it is possible to injure him. Should Interloper be injured somehow, he could regenerate any injured or missing tissue. However, if his mental control over his bodily molecules is broken or severed, he can die if recieving a fatal injury, that would otherwise not be fatal to him if he had his mental control, because his accelerated healing powers would not function properly.
- Flight: Like all Eternals, Interloper can levitate himself by mentally manipulating gravitons (subatomic particles carrying the force of gravitational attraction between atoms) around himself. Whereas Eternals ordinarily use their self-levitating ability to fly, Interloper has used it to walk on water. Interloper can also levitate other persons or objects, even while simultaneously levitating himself. The rate of speed at which Interloper can fly through levitation is unknown.
- Energy Manipulation: Interloper can project cosmic energy in the form of beams from his eyes or beams or flashes from his hands. This cosmic energy, stored in specialized enclaves of cells in his body, can be used as force, heat, light, and possibly other forms of electromagnetic energy. The full amount of energy that Interloper can release this way is unknown: it probably lies somewhere between the amounts that an ordinary Eternal can project (200 pounds per square inch of concussive force, 2000° Fahrenheit of heat, both effective over a range of about 175 feet) and the higher levels that the Eternal Ikaris can project (500 psi, 3000° F, both over about 200 feet). The expenditure of cosmic energy in this way continually for several hours will temporarily deplete Interloper's physical strength, but not his resistance to injury, although it will temporarily increase his sensitivity to pain. He will rapidly return to normal after such lengthy energy expenditure is over.
- Psionic Capabilities:It is not known whether Interloper can psionically create illusions or manipulate atoms and molecules. He can psionically teleport himself, but prefers not to do so, finding the process physically unpleasant. Interloper can psychically induce fear in the minds of other people whom he is near. His victims need not see him in order to feel the fear he projects; in fact, he can thus so terrify them that they become too frightened to turn around and face him. He chooses to project his fear-inducing power through his cloak.