The underwater civilization of Atlantis exists today on Champions Earth. It has a rich history and culture within the setting, summarized on pp. 93-96 of Champions Universe, and much more extensively detailed in two other books for the PnP game: Hidden Lands, which describes modern-day Atlantis; and The Atlantean Age, the antediluvian era when the island of Atlantis was the greatest power in the world. This background has considerable potential for character creation, but I've rarely seen anyone connected to Champions Online playing a character with an Atlantean connection. I suspect that's due in no small part to many MMO players not being familiar with Champions Atlantis. While I can't begin to transcribe all the available information here, I thought I would offer an overview which may inspire other members of the community to make their own Atlantis-derived PCs.
Between the years 35,000 and 30,000 BCE, the island nation of Atlan'elos rose to rule most of the surface of the Earth. It achieved this primarily through the tremendous magical spells and weapons wielded by its wizards and warriors; and the special blessings granted the Atlantean race by their gods, including divine blood in a not-insignificant fraction of the population. During this period the empire of Lemuria was Atlantis's chief rival for control of the world.
Pride and jealousy led to divisions in Atlantean society, culminating in a terrible civil war which unleashed a magical Cataclysm devastating the planet and reshaping the very continents. The human race was decimated, and civilization collapsed. But a few Atlanteans remained faithful to their traditional ways, and were saved by their god Poseidon. The god transformed them to be able to survive underwater, but they were no longer able to breathe air.
Some of these survivors decided to try to rebuild their society on the remains of their capital city of Atlantis, choosing a man named Glaucus as their king. Others left to make their own way in this new world. Over the succeeding millennia contact between Atlanteans and "Landers" was rare, and Atlanteans developed an isolationist, xenophobic mind set.
In the late 19th Century the king of Atlantis, Oceanus, realized that advances in Lander technology meant his people could not remain hidden from them much longer. He began to try to persuade his subjects to accept the concept of peaceful contact with the surface world. His policy deeply divided public opinion. An influential Atlantean named Dargon feared Lander technology, but also desired to conquer the surface world. In 1937 Dargon led a rebellion and killed Oceanus, claiming the throne for himself. Dargon secretly made an alliance with Germany, and his agents assisted the Axis during World War II.
Oceanus's daughter Mara escaped Dargon's rebels and fled to the surface. She eventually became known as a superhero called the Sea Hawk, and joined other heroes in the war effort. With the help of her super allies Mara overthrew Dargon in 1943 and became queen of Atlantis. She continues to rule today, despite a brief coup by one of Dargon's lieutenants in 1968, which led to an Atlantean attack on New York (the first time the wider world became aware Atlantis was more than a myth). Mara has continued her father's policy of opening Atlantis to the rest of the world, and in 1970 established formal contact with the United States and the United Nations.
Mara's son and heir, Prince Marus, studied for a time at Ravenswood Academy (the setting's school for super-youth, outside Millennium City) and served as a member of the renowned New York-based hero team, the Sentinels. However, his sister Thalassa was jealous of him, and her secret exploration of forbidden dark magic led to her becoming the supervillain Stingray, and to scheme to make herself Queen of Atlantis.
Modern Atlantis is a city-state of about 100,000 citizens situated in the middle of the Atlantic Ocean, 250 meters below the surface. Atlantis is not a member of the United Nations, but has observer status there and is recognized as a sovereign state by most surface nations. There are also thousands of "barbarians," descendants of those Atlanteans who left the city in its earliest days. Over a dozen tribes are scattered across the Atlantic, often squabbling over territory. Those nearest Atlantis have some sort of diplomatic relations with the city; others attempt to raid it from time to time. There are also smaller tribes of barbarians in the Pacific and Indian Oceans, and one band of hunters under the North Polar ice cap.
Some governments and others are very interested in Atlantis due to its unique resources and strategic location.
Atlanteans resemble humans in general form, although as a society they're more physically fit than Landers. They have skin and hair ranging from dark green to light blue-green, with hair typically darker than skin. They tend to have stereotypically Roman features. (Stingray's finned appearance in Champions Online may be attributable to the magic she used to augment her body's powers.) Atlantean clothing, armor and weapons, and art and architecture are reminiscent of classical Greece and Rome.
Besides breathing water, Atlantean bodies are adapted to the pressure, cold, and darkness of the depths. They live around a century on average, and members of the nobility can live much longer due to their divine bloodlines. Oceanus was over two hundred when he was killed, and Mara today looks barely middle-aged despite being more than ninety. Although their race as a whole isn't otherwise superhuman, the divine magic inherent in Atlanteans sometimes generates additional "magical mutations." The most frequent of these is the capacity to breathe air as well as water, called "Atlan's Gift." Other common mutations include enhanced senses; increased strength and toughness, sometimes to a major superhuman level; and the ability to communicate with and control sea animals. However, other random powers are known to manifest. For example, both Mara and Marus can fly, and Mara's voice can generate a potent sonic blast. Stingray used magic to imbue herself with the abilities of other sea creatures, including firing bolts of electricity.
Atlanteans are usually conservative, favoring order and tradition. Most are highly distrustful of outsiders, although there have always been Atlanteans curious about the surface world, particularly those with Atlan's Gift. They have a martial tradition -- more so among the barbarians -- but aren't particularly violent. Atlantean society is strongly stratified between the ruling nobility, the priesthood of Poseidon, and the majority common folk.
Atlanteans are still fundamentally human, and can interbreed with Landers, although such liaisons are rare. Half-breeds can inherit some of their Atlantean parent's abilities.
Most of the tremendous magical knowledge of ancient Atlantis (see below) was lost following the Cataclysm. The need to survive led the Atlanteans to focus on simple and practical spells, and the kind of potent magic which led to the Cataclysm was distrusted or outright banned. But small secret cults preserved fragments of that lore to the present day, including the wizard Nereus who served Dargon the usurper, and whose grimoires were discovered by Stingray. Rumors persist of vaults beneath the city of Atlantis undiscovered since the Cataclysm, holding the troves of the great wizards of the past. One reason Dargon allied himself with the Axis nations was his belief that secrets of Atlantean magic remained hidden on the surface, which would give him the power to conquer it. Champions lore would seem to support his belief; the present-day wizard called the Demonologist, leader of the Devil's Advocates supervillain team, discovered and tried to use an Atlantean spell, but his mistake in casting it created the fearsome earth-monster called Terrayne.
Given the global scope of Atlantis's empire, such troves of magic might be uncovered anywhere in the world.
In their heyday Atlanteans commanded some of the most powerful and sophisticated magic the world has ever seen, able to reshape their environment to a degree rivaling, and sometimes surpassing modern technology. Most of their magic spells involved control of elemental forces: not just the traditional Air, Fire, Earth, and Water; but also Light (and its opposite, Shadow); Order (and its opposite, Chaos); and Arcane, or pure magical force, the rarest and most difficult to master. Shadow and Chaos magics were considered evil and corrupting to use.
Atlantean mages were also masters of enchanting various items with a wide array of powers. Minor items were relatively common, but some artifacts were extremely powerful. They included the armor and weapons wielded by Atlantean warriors; wands, staves, rings and other talismans; articles of clothing; even vehicles such as flying chariots and ships, as well as buildings and other large structures.
Much of the power of Atlantean magic was based on oricalchum, a copper-colored metal found only on the island of Atlan'elos. (There are active oricalchum mines near the modern city of Atlantis.) Oricalchum takes and holds enchantments extremely well, making it ideal for fashioning magic items. More importantly, it can function as a magical power source -- the mightiest spells and artifacts were "fueled" by oricalchum. Steel alloyed with oricalchum is incredibly strong, but the oricalchum loses some of its magical properties in the process.