From Unofficial Handbook of the Virtue Universe
Tonatiuh is the avatar of the Aztec god of the sun, chosen in desperation so that the god would not vanish from existence. An often-times sardonic young man, Tonatiuh goes into the hero business willingly and enthusiastically but begrudges being saddled with a chatty and overbearing god, grinning everywhere he goes to hide the slow burn of bitterness.
Steve Skylar's life was relatively ordinary leading up to gaining his powers, in a sharp contrast to the cavalcade of rape and abuse that it seems many heroes suffer in their past. He was born to two perfectly loving parents in Modesto, California, formed a close bond with his three-years older brother Derek, and lived without ominous portents or shadowy figures guiding his path. While Derek was athletic, Steve proved to be something of a scholar, scoring consistently good grades all through high school. An early childhood love of dinosaurs blossomed into a general curiosity about the past, and once Steve graduated college he was all set on the path of archaeology.
Steve did not actually prove to be a dynamo of discovery - specializing in Africa, he uncovered many mundane things of tribes long past, but the big discovery always seemed to be just over the hill. He did, however, quickly become an expert in the procedures, and could be relied upon to organize any kind of excavation, ensuring that the precious history was preserved as well as could be. It was for this reason that the young man was called away to Central America during a particular lull - someone had unearthed an important-looking temple, and as he wasn't busy, it was determined that his expertise would be useful. Steve oversaw the excavation admirably, though somewhat jealous that it wasn't his own discovery, and everything went perfectly until one fateful misstep.
It's entirely possible that Steve Skylar's slide into the temple proper was not actually an accident, but rather the desperation of Tonatiuh, fearing his existence should the number of people who remembered him continue to decrease. Before Steve even knew what was happening, the voice of Tonatiuh drove into his skull: "LONG HAS IT BEEN SINCE ONE HAS COME TO PAY HOMAGE TO ME, AND MY INFLUENCE HAS WANED FAR TOO MUCH IN THE WORLD. I NAME YOU, CURIOUS DIGGER, THE BEARER OF MY POWER, TO REMIND THIS WORLD THAT I EXIST AND THAT I WATCH. NOW, TAKE THIS, THE POWER OF THE SUN!" A tremendous fire swirled into his body from everywhere at once, forming the sun that burns on his chest, and the pain and shock sent Steve into a coma from which he did not awake in three years. During this time, his brother died in a car accident, a fact that occasionally weighs on Steve's mind.
Once Steve awoke, it took him a long time to cope with everything that had happened and even longer for him to convince himself that he was not insane and actually had a god in his head talking to him. It wasn't until he was sorting through Derek's things and found a collection of action figures depicting the Surviving Eight that Steve realized what he could do with his newfound powers, shaking out of his funk and travelling to Paragon City.
Tonatiuh is a member in good standing with the Paragon Defense Authority, and former head of the short-lived Northern Light.
Tonatiuh has no known enemies, but believes it to be very possible that other Aztec gods intend to do what Tonatiuh has done, and he therefore has a wide range of hypothetical allies and enemies.
Power of the Sun
Tonatiuh is capable of drawing directly on the sun, essentially teleporting relatively miniscule portions of it to his body and channeling it outward. While this would theoretically render Tonatiuh immune to the sun itself, ordinary flame is unhindered. He is able to use this power in a variety of ways, from simply throwing it outward in great gouts to encircling foes to simply glowing with the sun's radiance. (Fire Blast, Fire Manipulation)
Though normally Steve Skylar chooses to suppress the Sun God as much as he can, when pressed he can allow Tonatiuh's true splendor to influence the area, throwing those who oppose him into terror and panic. (Presence)
Path of the Sun
Tonatiuh is capable of reaching through small sun 'portals' to bring people to him from afar, although he cannot move through these portals himself. Though the portals appear to be discs of bright flame, they give off only a comforting heat, and do not affect anything otherwise. (Recall Friend)
The Sun's Journey
Tonatiuh is capable of traveling at high speeds by turning into a large yellow fireball, and hurtling himself through the air in a pattern reminiscient of the sun's rising and setting. (Super Jump)
Tonatiuh is immune to almost every kind of disease, poison, and malady under the sun in the long term, as the sun god's power purifies his body every hour of daylight and every two hours of night. However, in the short term Tonatiuh still feels the effects of these things, and powerful poisons can render him unconcious until the next purification.
As long as Steve Skylar is host to Tonatiuh's power, he will not age, and will prove very difficult to be truly killed by a mortal. This hasn't quite sunk in yet, and he tends to get very quiet when it comes up in conversation.
When Steve Skylar sleeps during the day, or enters either the Spirit World of Croatoa or Dark Astoria, Tonatiuh himself is capable of asserting control over his avatar's body, altering his form. Once Tonatiuh has managed to assert himself, Steve has no memory of anything during the sun god's emergence. When exceptionally pressed, Steve may give his body over to Tonatiuh willingly to benefit from his greater experience, though there is no guarantee that Tonatiuh will return the favor when the problem is solved. Unless in the Spirit World or Dark Astoria, Tonatiuh cannot posess Steve's body at night. Tonatiuh is also incapable of posessing Steve in the Pocket D, though Steve does not know this.
While Steve Skylar himself is unskilled in any field aside from archaeology, the guidance of the Aztec Sun God effectively enables him to do a wide variety of tasks well, provided they aren't too modern. As a result, Tonatiuh is effectively very skilled in such things as single combat, war strategy, hunting, and surviving in the wilderness. However, most of these are completely useless in Paragon City.
He is also posessed of an incredible aura sense, capable of detecting many things those less powerful than him may be trying to hide, and can feel anyone with arcane talent from at least 500 feet away. Fortunately, Tonatiuh is polite enough not to openly discuss what others obviously wish nobody to know about.
Disadvantages of Being Divine
Being the avatar of an Aztec god carries with it a wide variety of little disadvantages, few of which actually impair Steve Skylar in combat but make his life aside from heroics quite difficult.
Linked to the Sun
Many of Tonatiuh's powers become harder to use once the sun has set, and he feels an intense compulsion to sleep until sunrise. This is by no means an absolute limiter, however. Conversely, as noon approaches, everything seems to get easier for Tonatiuh, and he is typically in a very good mood - and the height of his power - by noon.
As Tonatiuh had gone many years without anyone listening to anything he had to say, the sun god constantly weighs in on every situation Steve finds himself in, frequently distracting the man and causing him to act somewhat impulsively. Steve suffers from a constant mild headache when nothing else is aggravating it, and takes aspirin at a constant rate.
The Aztec pantheon is notorious for demanding sacrifices as a whole, and Tonatiuh was one of the most sacrificed-to deities among them - according to Aztec belief, the sun would not move across the sky without sacrifices. Tonatiuh has therefore become accustomed to this, and constantly demands that Steve take his fight against crime farther. Though he has yet to actually kill anyone (aside, of course, from robots and Vahzilok zombies), Steve fears that one day he may lose control and Tonatiuh will have his sacrifice.
In the presence of particularly powerful - or any divine - auras, Steve's headache worsens to a near-migraine, making it difficult for him to concentrate on anything and making it easier for Tonatiuh to influence him.
Mark of the Sun
A tiny sun blazes from Tonatiuh's chest, showing through anything he wears and burning most regular shirts to a crisp. Unless he puts a substantial amount of effort toward subduing it, the sun gives off light and heat much like a powerful torch would, and renders stealth a non-option. Tonatiuh is also incapable of maintaining a secret identity, as the blazing sun is instantly recognizable and cannot be hidden except by powerful magical darkness - which is itself highly conspicuous.