Otherworldly

Aliens, mythical creatures, gods, and other such beings are treated with skepticism and doubt. Even though their powers might be demonstrable, and nobody doubts they can do incredible things, trying to accept their origins as stated is simply too far for most to deal with.

Nonetheless, these individuals do exist and some have been known to become costumed super-heroes or members of SHIELD, including the Avenger known as Thor.

These individuals aren’t just people who were altered by science, technology, or so-called magic that have a gimmick or identity that implies they’re some kind of supernatural being (like John Horton, the genetically altered criminal who calls himself the Griffin). They are what they say they are, at least insofar as they know and understand or choose to present.

A few notable examples of otherworldly beings that you might be (or at the very least, claim to be) are below.

The Myth

It’s possible that Earth’s various myths and legends might have some kind of truth to them. More open-minded scientists and historians who believe such things are possible still usually conclude that these beings were likely extranormal individuals of their time, who had incredible powers that the people of those eras could only attribute to the gods or monsters.
But with people like Thor running around, those kinds of skeptical doubts are really difficult to maintain, and perhaps there really are mystical creatures of myth and legend that really exist.
Asgardians: Currently, the only individual on Earth who makes at least a somewhat credible claim to be from the mythical realm of Asgard is the Avenger known as Thor. It’s possible there are other Asgardians out there, if Asgard is a real place and Thor is being honest about his origins. There’s a multitude of other races from Norse myth who might also be real, such as elves, dwarves, and frost giants.
Olympians: There are no known, documented examples of these beings in modern times, but in theory if Asgard is real, then possibly Olypmus is real too. If so, there could be demi-gods and other creatures of Greco-Roman myth walking the Earth, like centaurs, satyrs, or titans.
Vampires: Vampires are just stories. At best, there might be an extranormal individual created by mad science who emulates the tropes and abilities of a vampire, such as the scientist Michael Morbius. Vampires aren’t real… or are they?
Werewolves: Shapeshifters are real. In modern times, there are extranormal individuals who have been genetically engineered or altered by science and do have the ability to change their form. But classical lycanthropy, actual for-real werewolves, are scoffed at and disregared as myth. Perhaps the myths have some grain of truth, however.
Angels: As skeptical as people are of Thor’s claim to be a god of Asgard, a person claiming to be a literal, Biblical angel would be met with even greater skepticism and scrutiny. The existence of such a person, if their origins were true, would have far-reaching implications for theology and global religious conflict. Any person who publicly made such a claim would likely find themselves quickly scooped up and concealed by SHIELD, lest they incite some kind of public theological panic.
Demons: Similar to the issue present with a person who supposedly claims to be an actual angel, a person who claimed to be a literal demon or possessed by a demon would be met with not only skepticism, but a need on the part of SHIELD to keep them from making such public claims. Likely, a person claiming to be a demon would be imprisoned for public safety, but if they were thought to be trustworthy (or at least controllable) they might be used for STRIKE.
The Fey: A variety of largely European myths and legends talk about fairies, sprites, and other such creatures. While no known examples of individuals claiming to be such things exist, that doesn’t mean they couldn’t.
Atlanteans and Lemurians: There’s a myriad of different “lost continents” and islands of myth in Earth’s legends. Atlantis, Lemuria, Mu and other such places have no historical evidence to suggest they ever existed, and there’s no credible claims put forth by individuals who purport to be from those places. But there could be, and if there were it’d be a pretty huge concept for modern geographers and historians to wrap their heads around.
Devas and Asuras: The gods and demons of Hindu myth have no known, modern examples suggesting they really exist. Hinduism is a massive religion, with billions of adherents, so a person who claimed to be a Deva or worse yet, an Asura, would be a serious subject and could present a serious conflict for billions of people. Much like a person who claimed to be a Judeo-Christian angel or demon, SHIELD would likely conceal the identity of a person who made such a claim, and might use them for STRIKE depending on the situation.

Suggested Origins: I’m A Freak, I’m Back From the Dead, The Beast Inside Me, My Alien Heritage, What I Carry, What I Know
Suggested Drives: Adapt to a Changing World, Inspire, Figure Out Who I Am, Understand Humanity, Start Anew

Example Characters: Thor, Sasquatch, Wendigo, Hannibal King, Namor

The Alien

Thus far, there’s been no verifiable, 100% irrefutable proof of extra-terrestrial life from outer space even existing, let alone making contact with Earth. There have been individuals like Hyperion who claim to be the last survivor of an alien race, sent here as a baby and growing up on Earth, but there’s no verifiable proof to his claims beyond the fact that he has extranormal powers. He doesn’t even look different from a regular human.
SWORD’s entire existence as an agency is to find (and potentially defend against) alien life. They would work very hard to control information about the existence of extra-terrestrial life so as not to create a public panic, so it is unlikely that a person who has at least a reasonable claim to be an alien would even be working for STRIKE (they’d more likely to be under direct observation and control of SWORD). But, in theory, it’s possible, especially if such a person wasn’t 100% honest about their alien origins.
Below are a list of possible approaches your character could take to being an alien, rather than specific alien races to choose from. If you choose to be an alien, work with the GM as to the specific nature of your race.

The Last Survivor: Hyperion claims to be the last of his race, jettisoned to Earth as a baby when his planet was on the verge of destruction. He might not be the only member of his (unnamed) race sent here, or there might be other varieties of aliens who sought refuge on Earth due to some calamity on their own world.
The Emissary: Your race might be some vast star empire or at the very least capable of interstellar travel, and they’ve sent you as an envoy to Earth. If that were the case, SHIELD would keep your message under wraps, because SWORD would determine you could incite a public panic. Depending on your abilities and motives, you might find yourself employed in STRIKE.
The Renegade: Perhaps you are fleeing your world because you’re a criminal, rebel, or otherwise don’t fit in with your society. Earth is a sanctuary for you, a place very different from your homeworld. You might not be honest with SHIELD about your alien origins, and they might not be aware of your criminal past either.
The Explorer: You are an alien explorer, a scientist or academic who has come here to learn about our world and its people. You might be upfront about your alien origins, or perhaps for reasons of some higher directive or scientific principle you conceal the truth of what you are so as not to rile up the locals.
The Marooned: You didn’t mean to be here, but you’ve crash-landed on our world or otherwise found yourself unable to leave. Perhaps you’re working towards a solution that will let you go home, or maybe you gave up on that long ago and are just making a new home for yourself here. You may or may not tell people you’re an alien, and STRIKE might be a means to an end towards your goal or something you truly believe in.
The Conqueror: You came to Earth (or were sent here) not as a diplomat or researcher, but as a conqueror. Perhaps you are the vanguard of some alien army, or your species believed you alone were enough to take over the world. Do you still have this goal, or have you come to care about Earth and reject your mission?
The Guardian: You are Earth’s protector. Perhaps you assigned this task to yourself, or you’re part of some larger interstellar protective force. Maybe your mandate originally was only to protect Earth from extra-terrestrial threats, but now you’ve seen the dangers on the planet itself and it motivates you to help. This may or may not be in violation of a directive about non-interference that your species or organization assigned to you.

Suggested Origins: I’m a Freak, The Wake-Up Call, My Alien Heritage, My Mission, What I Carry, What I Know
Suggested Drives: Become an Icon, Create, Inspire, Figure Out Who I Am, Lead, Protect, Push the Boundaries of Science, Rebel, Start Anew, Understand

Example Characters: Hyperion, Captain Marvel

The Machine

True Artificial Intelligence is something a lot of agencies, corporations, and researchers are working on, but thus far none have truly crossed the threshold into something sentient and sapient. There are robots, even humanoid robots, that do exist but they’re thus far drones who need to be controlled remotely or automaton servants who are obviously non-sapient.
But we’re on the verge of that discovery, so at any point someone might cross the line and create a true AI. Such a creation would have far-reaching implications for a variety of fields, and have deep philosophical, ethical, and moral questions their existence raises.
As a result, if such a machine was created, SHIELD would likely try to both control it and conceal its existence from the world at large, and STRIKE might be a way for the agency to put it to work.
Below are a few groups and individuals who might be responsible for the creation of a sapient machine intelligence.

SHIELD: SHIELD’s SCI-TECH division has been working on various robots for a long time. They themselves might have stumbled upon such a discovery.
AIM: AIM has no boundaries to their research, including ethical ones. They create relentlessly, doing what they must because they can. An AIM-created machine intelligence might rebel against its masters, or have been seized by SHIELD before it could do harm.
Future Foundation: One of Reed’s projects involves creating robotic servants. While he’s not intentionally trying to create true artificial intelligence, it might be the errant result of one of his experiments.
Stark Industries: Stark Industries has produced a number of robots for domestic, military, and commercial use. Thus far, they’ve all been non-sapient drones. It’s rumored that JARVIS, the internal operating system that Tony Stark uses for his Iron Man armor, is actually a true AI, but Stark denies this. Still, it’s possible a derivative of JARVIS or some other Stark project might cross the threshold.
Cybertek: While they’re focused largely on cybernetics and man-machine interfaces, Cybertek’s cutting edge research might have resulted in a machine intelligence they didn’t account for.
The Fixer: Paul Ebersol is a dangerous criminal mastermind who creates all sorts of technology for super-villains, most of it being cybernetics or power armor. However, he does use robots, and it’s possible he might create a sentient machine, intentionally or not.
Latveria: Doom’s regime is known for using robotic drones in addition to their power armor. Doom is one of the world’s most brilliant roboticists, and has created incredible machines. According to SHIELD intel, Doom himself might use robotic duplicates as body doubles in case of assassination attempts and so that he can further extend his reach. These doubles would have to be incredibly advanced, and possibly sapient in and of themselves, to pass for Doom himself. Perhaps one of Doom’s creations goes rogue and defects to SHIELD?

Suggested Origins: The Accident, My Mission, What I Carry
Suggested Drives: Create, Figure Out Who I Am, Protect, Rebel, Start Anew, Understand

Example Characters: Ultron, Vision, Arsenal

Otherworldly

Agents of STRIKE MattZenith MattZenith