There is more complete information on this topic on the spoiler page.
Scion travels from place to place at supersonic speed, helping people. He doesn't seem to rest or take breaks.
Although his face is expressionless, he somehow communicates emotion to others. When he first appeared, he radiated sadness. He seemed to radiate disgust when looking at Eidolon.
He was only known to have spoken once - when he gave his name to a Russian woman. However, he was believed to have a human contact somewhere. The heroes had no way to contact him, having to simply hope that he would notice when they were in a dire situation and intervene.
Scion appears as a burnished gold man with long hair and a short beard. He had no body hair. His eyes were the same featureless gold as the rest of his body. He glowed with a golden light that caused water to wick off his hair and body, and cleaned and dried his clothing. It left a brief trail in the air when he flew.
His expression never changes, but onlookers somehow perceive his emotions anyway (see above), which often leads them to describe him as looking sad.
When he first appeared, he was naked. At some point, he donned clothing. At first, a sheet worn over one shoulder and pinned at either side of the waist, then more conventional clothes. In 1999, he donned a white bodysuit extending to his biceps and toes. He doesn't wear shoes or gloves, but his costume did include a plain white cape. His clothing was often filthy, but would slowly but surely clean itself over time, causing the stains to fade as dirt and particles were pushed out of the fabric.
There is more complete information on this topic on the spoiler page.
Scion was considered the most powerful individual in the world. His powers were so strong that they put him "head and shoulders" above everyone else, with the exception of the Endbringers. He was even powerful enough to defeat an Endbringer, the only hero who could do so except for Eidolon.
Scion's primary power is the power to negate any kind of wavelength using his golden light. This effect is extremely versatile; it can be used to disintegrate matter, slow or stop motion, and negate the effects of specific powers. Stilling can be fired as beams, orbs, or area bursts, used as a force field, or transmitted by touch. When used offensively, the effect lingers, continuing to eat away at the target after the initial attack. Offensive blasts range greatly in power, from thin beams to continent-destroying blasts.
Scion can fly at immense speeds as an application of his general golden light aura. At his fastest, he was able to fly to the other side of the world in less than a minute. He left a short golden trail in the air.
Scion is immune to certain types of powers. His actions cannot be predicted with precognition, his powers cannot be copied, and powers cannot directly interfere with his mind in any way. In addition, his multiple senses make him very difficult to blind or mislead for any period of time.
Scion can "tune" his defenses to defend against specific powers (see Stilling.)
On May twentieth, 1982, Scion was seen by a boat, whose passengers started to try to talk to him. He was touched by one passenger who was dying of cancer, this cured him. Then, he turned away from the crowd and flew away.
He then spent years wandering the world, observing stopping at places. Even listening sometimes. Eventually he began helping people, getting faster and faster. By the middle of the 1990s, he was traveling from crisis to crisis, flying faster than the speed of sound. He Also took to wearing cloths and by 1999, had seemingly taken to wearing a white bodysuit that was kept clean.
At one point Scion came across a burning town and began to exterminate each source of heat. He lowered himself to get a better shot at the library and came into contact with a woman reporter who asked him his name. He answered her that his name was "Scion". It is the only time Scion is known to have spoken.
Additionally, Scion once reacted to a nuclear test in the same way he had been reacting to paramilitary groups in Africa and the Middle East, shooting down a test missile and destroying the launch facility. This convinced nuclear powers that Scion would intervene, effectively ending the Cold War.
He took to fighting the Endbringers, and was one of the only people who could stop them.
Scion showed up for the Endbringer attack on Brockton Bay and was able to drive the creature away.
↑Capes with the ‘breaker’ classification were generally those who had some ability to ‘break’ the natural laws of the universe as far as those laws applied to them. Shadow Stalker was one. Scion was apparently another. - Excerpt from Sentinel 9.2
He maintains a toolkit [...] thinker abilities to understand complex ideas/languages, the precog ability that costs him a lot of lifespan to use, and a bunch of other stuff I can't be arsed to name, as I said above. - Wildbow on Spacebattles
↑ 5.05.15.2We were hoping for Scion. The first cape, the golden skinned man. The guy that could go toe to toe with an Endbringer and win, if things hadn't already gone too far south. [...] The problem with waiting on Scion was that the guy wasn't exactly in touch with the rest of us. There was speculation he had at least one human contact – someone that had given him clothing and a costume, at least – but he never bothered to stop long enough for anyone to pass on any requests, to tell him to go to X place when we gave him Y signal. He rescued people twenty-four-seven, three hundred and sixty five days a year, handling crises only as they came to his attention, which meant that sometimes an Endbringer came and Scion was wholly occupied with saving sinking ships, stopping landslides and putting out housefires. - Extermination 8.4
↑ 7.07.1Scion paused, turning to look at Eidolon, his eyes moving past Bitch and me like we weren't even there. His eyes settled on the hero, the most powerful individual in the world staring at the man who was arguably the fifth.
His expression was so hard to read. I knew, now, what people had meant, when they said they thought his face was a mask, a facade. Though it was expressionless, though there was nothing I could point to to explain why I felt the way I did, somehow I sensed disgust from him. Like nobility looking at dog shit. - Extermination 8.5
↑We stall, from here on out we prioritize survival over putting this abomination down, and we fucking pray that Scion notices there's an Endbringer around and shows up before this city and everyone in it is a memory. - Extermination 8.3
↑When the question inevitably got to who was the strongest, the ‘big five' were generally ruled out, in the sense of ‘well, yeah, but besides them‘. Scion got counted as a part of that group because the powers he did have were head and shoulders above just about everyone else's. Eidolon was almost the opposite, because he had every power, though he could only hold on to a handful at a time. Then there were the Endbringers, because they mandated situations like this, where even Scion or Eidolon plus multiple teams of capes weren't necessarily enough. - Extermination 8.1
↑Against the Endbringers, there are really only two individuals who can stop them, drive them away. Scion is one. I'm another. - Interlude 18.z
↑ 14.014.1Scion equipped himself to be able to fight pretty much any threat. His big weapon is a very versatile 'stilling' ability, which lets him cancel out wavelengths, which can be applied in a variety of ways, defensive or offensive - it lets him counteract, manipulate, and cancel virtually any parahuman or human generated effect. He can cancel out heat, eliminate sound, break Grey Boy's ability, disintegrate molecular bonds, etc. He can do so with beams, thrown orbs/bullets, a light he emanates, and a personal forcefield, among a variety of other mechanisms. - Wildbow on Spacebattles
↑He came out swinging, obliterating two continents on two different worlds before he found us.
-Excerpt from Speck 30.5
↑ 16.016.1When Scion uses his power it disturbs electronics. Its why when he flies you can't track him unless its with your eyes.
- Excerpt from Interlude 24.y
↑Eidolon used his matter creation power. As with the Faerie Queen's monster of steel, this was derived from a single point, an expanding creation of matter. In this case, however, it was an explosion. Carbon unfolded from a single point. Eidolon chose Scion's right ear canal as the center point.
The carbon expanded as a sphere, and there was a glimmer of Scion's reaction as the orb expanded until it was a hundred feet across. A distortion, golden flesh stretching.
The sphere dropped towards the ocean like a comically large cannonball, and Scion advanced. Intact, unhurt. - Interlude 27.x
↑"Because we aren't hurting him," I spoke my thoughts aloud. We haven't touched him.
"We're hurting him," she said. "Kind of like how people hurt Gavel. He's… he's got a defense, not making him invincible, but making him a living portal. So you hurt him, and faster than you can do anything, he just swaps out the damaged material for material from… this bottomless well." - Venom 29.2
↑"The first way, you've got to be basically immune to powers. Scion is. He's immune to precognition, throws everything out the window when he shows up. I saw it when he fought the Simurgh. She couldn't automatically dodge his stuff, because she either couldn't read his mind or she couldn't see the attacks before they happened. So he hit her, a bunch of times. I saw it." - Migration 17.8
↑Scion blasted the cliff faces, but his golden light only affected the cliff on this earth. The moment he stopped, more emerged.
He stopped to strike again, this time obliterating the cliff faces on this Earth and the one in the other reality. - Excerpt from 27.x (Interlude, Eidolon)