Because this subject was recently inquired into on the main Champions Online website discussion forums, I thought it would probably be appropriate to post info here about this notable Champions Universe organization; particularly in relation to its potential for Player Characters. I'll just start by saying that, while I'll be happy to answer questions about the Star*Guard within the limits of Fair Use of the IP, the Star*Guard has an entire chapter devoted to it in the book, Champions Beyond, which describes in great detail the "space" side of the Champions Universe -- alien races and civilizations, individual NPCs heroic and villainous, cosmic entities, and the like. That chapter details Star*Guard history, structure, technology, major enemies, and types of StarGuards (the term "Star*Guard" refers to the organization as a whole, while "StarGuard" designates an individual operative).
In many ways the Star*Guard is analogous to the Green Lantern Corps from DC Comics. It exists to protect sapient life in the Milky Way Galaxy from all manner of threats, to foster cooperation between civilizations, and to help integrate species into the wider galactic community; but doesn't involve itself in "local politics" (which can even include interstellar wars, depending on the circumstances). Individual StarGuards may be recruited from any sapient species in the Milky Way. They're intensively trained on the Star*Guard's home base, the planet Odrugar, and given an extraordinary technological weapon, the Star-Staff. Once their training is complete a StarGuard is assigned duties, most often as the guardian of a particular "sector" of the galaxy. The current StarGuard for Earth's sector is a Human, a Spaniard named Andre Almena. Almena is featured on the center of the cover of Champions Beyond: https://content.invisioncic.com/s285913/packages-0614345001387422035.jpg
A million years ago the Odrugarans were the most advanced species in the Milky Way. At that time their greatest genius and hero, Gloran, was born. Gloran used his gifts to become a superhero, battling evil both to protect his people and other worlds in the galaxy. He created an incredibly sophisticated AI computer, called CONTROL, to assist him, and recruited other heroic individuals to fight alongside him. That was the genesis of the modern Star*Guard. When Gloran died his knowledge, memories and personality were downloaded into CONTROL -- this has become the pattern for preserving other notable StarGuards and Odrugarans after death.
Over the eons Odrugaran society has shaped itself to support the work of the Star*Guard, and CONTROL became the benevolent ruler of the planet and director of the Guard, assisted by an appointed Council of Overseers (many, but not all, former Guards themselves). CONTROL possessed telepathic systems enabling it to communicate directly with StarGuards anywhere in the galaxy, and to scan minds to find worthy recruits. However, an attack on Odrugar by the treacherous former StarGuard, Mordace (more-or-less an analogue for Sinestro) in Earth year 2009 left CONTROL severely damaged, forcing the Guards to become more self-reliant. Based on the notes in Champions Beyond it may be that repair efforts on CONTROL still have not returned it to full functioning.
StarGuards assigned sectors to protect inhabit a Star*Base constructed for them with Odrugaran technology, usually well away from populated worlds to avoid collateral damage from enemy attacks. Andre Almena's Star*Base is on Jupiter's moon Europa. While a StarGuard can travel between the stars using their Star-Staff, they're also assigned one or more small advanced starships called a StarJet for when they want to transport multiple persons. They also have one to five Marshals assisting them in various capacities, living with them at the Star*Base.
While the majority of StarGuards protect specific sectors, others are assigned to specialized units within the Guard and sent to wherever they're needed. One of those groups is the StarScouts, trained in reconnaissance and diplomacy, whose Star-Staffs and other tech are optimized for rapid travel and communication. They often serve as scouts or couriers, particularly since CONTROL was damaged. If considered desirable, a new StarGuard may also complete their training by being sent to "apprentice" to a veteran Guard. Either of these options would be appropriate to introduce a StarGuard PC to Champions Online. Alternatively, a PC could be one of Andre Almena's Marshals, recently recruited to assist him on Earth. Marshals don't carry a Star-Staff, but may be equipped with other advanced tech.