The origins of the Runner are unknown. He is known to be the last survivor of a species who inhabited one of the first galaxies formed after the Big Bang; his galaxy (and planet) have since been destroyed. The Runner said once to Silver Surfer that he is five billion years. Notice that the Big Bang was approximately 13.7 billion years ago - thus the Runner is relatively young for an Elder of the Universe.
Apparently, the Runner found a key to immortality through an obsession for total freedom. He has said that, should he was forced to be captive on one planet, he would have died. He lives to become the first entity to see all the universe, having no other interest - which makes him seem frivolous. However, his attitude (probably enhanced with discreet uses of Cosmic Power) allows him to make friends with any person he meets. Due to his immortality, he joined the Elders of the Universe.
It is believed that any responsibility would interfere with his "path of freedom", no matter the cost. Recently, the Runner discovered that a star would become a nova in only one decade and told the Earthling superheroine, Moondragon. She suggested the Runner warn the inhabitants of the planets in that star system, but the Runner explained that this responsibility would interfere with his freedom, and thus, with his immortality.
The Runner worked alongside the Grandmaster and other Elders in a plot to kill Galactus and thus destroy the universe, causing the creation of a new universe where the Elders would become Galactus-like beings. Perhaps the finiteness of the universe in comparison with eternal life convinced the Runner to work with the Grandmaster - If the Runner truly sees the whole universe, he would face an eternity of boredom.
However, the Silver Surfer stopped the Elders' scheme. It was unclear what would happen now with the Runner.
As the Runner came into contact with Thanos who desired his Space Gem. A battle ensued in which Thanos used the previously procured Time Gem to accelerate the Runner's age to 1,000,000 years old.
Thanos traveled to the Collector to hand him in, but soon after the Runner turned back and began to attack the Collector.
The Power Primordial: The Runner's body has been imbued with a portion of the Power Primordial, which is residual energy left over from the Big Bang that created the current Marvel Universe. This energy manifests itself as cosmic energy that the Runner has spent countless eons channeling for certain purposes, such as granting himself superhuman attributes at various levels. The Runner has essentially trained himself over billions of years to channel this energy to grant himself the powers he's wanted and at what level he wants them. This makes the Power Primordial similar to the cosmic energy utilized by the Eternals, only to a much greater degree.
Superhuman Strength: The Runner has channeled a portion of the Power Primordial to grant him superhuman strength. The Runner is sufficiently strong enough to physically overpower beings such as Silver Surfer in battle.
Superhuman Speed: As his name implies, the Runner has devoted much of the Power Primordial to build up his speed. He can run, move, and think at incredible velocities. The upper limit of his speed isn't known and, while within the atmosphere of a planet that supports life or can support life, the Runner restrains himself to speeds well below his maximum. However, he has been known to run tens of thousands of miles per hour while on a planet with ease. It is believed that while in possession of the Space Gem that the Runners speed was increased but as confirmed by Thanos it occasionally allowed him to teleport to locations before he himself wanted to be there.
Flight: The Runner is also capable of propelling himself through the air or outer space under his own power. Although he is technically flying while doing this, he actually appears as though he's running. The Runner is capable of flying at speeds many times the Speed of Light, which is roughly 186,000 miles per second. He is arguably the fastest being in the Marvel Universe.
Superhuman Stamina: The Runner has also devoted a great deal of the Power Primordial to increase the efficiency of his musculature, which is infinitely superior to the musculature of a human being. The Runner's muscles produce no fatigue toxins during physical activity, granting him limitless superhuman stamina in all physical activities.
Superhuman Durability: The Runner's body is composed of a flexible metallic alloy that renders him practically invulnerable to conventional physical injury. He can withstand powerful impact forces, exposure to extreme heat and pressures, powerful impact forces, and can survive indefinitely within the depths of space without being injured. His body is also specifically designed to withstand the rigors and damage that moving at such extreme velocities could cause to the tissue of most other beings.
True Immortality: While many beings have claimed to be immortal, the Runner is one of the few beings that truly is immortal. As a result of the Elders of the Universe being banned from entering Death's realm by Death itself, The Runner is incapable of dying. While it is possible for him to be injured or rendered unconscious, his body can literally heal him from any type of injury, no matter how severe or how long it might take. Even without Death's edict of banishment, the Power Primordial has made the Runner completely immune to the effects of aging and all known diseases. He also requires no food, water or air as the Power Primordial energies are all that is necessary to sustain him.
Superhuman Agility: The Runner has channeled the Power Primordial to enhance his agility, balance, and bodily coordination to levels beyond the natural physical limits of the finest human athlete.
Superhuman Reflexes: The Runner's reflexes have been enhanced even further, enabling him to react almost instantaneously.
Energy Blasts: The Runner has also channeled the Power Primordial for the purposes of firing powerful blasts of concussive force from his hands. It isn't known if he can use these energy blasts for other purposes, such as generating intense heat, light or to rearrange matter on a molecular level. These blasts have proven powerful enough to harm the Silver Surfer in the past.
Psionics: The Runner has demonstrated a psionic ability to stimulate the pleasure centers in the brains of beings around them, essentially causing them to feel good or to feel at ease. The exact nature and full limits of this power aren't known, nor is it known if the Runner can consciously control it.
Although the Runner doesn't particularly enjoy combat, he has proven himself to be a formidable combatant. The sheer speeds at which he can propel himself simply make him too fast for most other beings to even attack him.
Prior to Death's banishment, the Runner's obsession with freedom and essentially seeing and experiencing all that there is, was responsible for his immortality. Should Death's banishment ever be lifted, and the Runner becomes bored with his life, it could potentially be fatal to him. Also without Death's banishment, it is possible for the Runner to sustain physical injury that the Power Primordial can't heal, resulting in his death.