Mystical

While most scoff at the idea of “magic”, or at best accept it as sufficiently advanced science we don’t currently understand, it’s nonetheless true that there are individuals who possess powers or wield artifacts that have no explicable origin but to call it magic.

The Member of a Secret Society

There are many secret societies through-out Earth’s history. Most are largely the same, in the end; a group of shadowy individuals collude to acquire, maintain, and expand their power. They’re largely mundane and often criminal organizations motivated by simple human greed. However, some secret societies are actually very powerful, and have over time accessed resources, relics, powers, and techniques that they probably ought not have.
A character who originates from these Secret Societies are probably a renegade of some kind, defecting to SHIELD to leave their old life behind.
Some possible secret societies you might hail from:
The Hand – An organization of ninjas originating from Japan, the Hand appear to be some kind of apocalyptic cult and engage in bizarre mystical practices in addition to martial arts. A former member of the Hand, code-named Reflex, defected to SHIELD in the 1980’s, so it’s not unprecedented for former Hand members to join SHIELD.
HYDRA – While largely thought of as an extension of the Nazi war machine in modern times, HYDRA is actually a secret society with its own occult beliefs separate from Nazism, and in fact predates the Nazi Party by a few years (or much longer, if you believe HYDRA rhetoric about them being an ancient order). HYDRA have done numerous experiments with “deep science” over the decades, and there are some who have lost faith in the group’s ideals.
Leviathan – Leviathan is a Russian secret society as old as the rise of Communism. They were SHIELD’s greatest foe during the Cold War, and while they prefer hard science to mysticism (unlike HYDRA), Leviathan are a secret society with their own mysteries.
The Ten Rings – A multi-national terrorist organization that is sweeping the Middle East and parts of south-western Asia, the Ten Rings are a secretive, elusive organization with some kind of devotion to a mysterious figure known only as the Mandarin.

Suggested Origins: I’m Back From the Dead, Wake-Up Call, My Mission
Suggested Drives: Do What Others Cannot, Prove Myself, Rebel, Reconcile My Past, Redeem Myself

Example Characters: Reflex, Baron Wolfgang von Strucker, Elektra

The Occultist

There are individuals who claim to be sorcerers, exorcists, witches, or other masters of mysticism. These people often have real, demonstrable powers, but the majority of the world remains suspicious that they may be con-artists trying to pass off an ability granted by science or technology as “magic”.
There are a few known groups or alleged sources of occult power that such a character could draw from.
Tibetan Sorcery: There is, according to legend, a secret temple in the mountains of Tibet where a mysterious order of sorcerers protect the cosmos and preserve the balance. According to rumor, Dr. Stephen Strange studied with them, but he is not the only individual who gained power there.
Ancient Traditions: Earth’s history is replete with different styles of shamanism, occultism, and other practices whose adherents claim to invoke supernatural forces. While some have been proven fraudulent, or have perfectly rational explanations for what they can do… some are true mysteries.
Forbidden Knowledge: There are some who claim to possess understanding of methods of mysticism older than recorded history, from fallen cultures and lost civilizations that may or may not be fictitious.

Suggested Origins: I’m Back from the Dead, The Deal, My Mission, What I Know
Suggested Drives: Inspire, Lead, Protect, Understand

Example Characters: Dr. Stephen Strange, Baron Mordo, Daimon Hellstrom, Iron Fist, Hellfire

The Artifact Bearer

There are items of great power through-out history, most of which are considered objects of myth and nothing more. However, some individuals claim to wield artifacts of unproven origin that seemingly grant them incredible power.
Here are some possible sources of such artifacts that your character may have come to possess:
Ancient Blades: While Excalibur is arguably the most famous sword of myth and legend, there are other such weapons that are unaccounted for, if they ever existed. Almace, Cortana, Durendal, and Joyeuse from the age of Charlemagne. Gram, Hrunting and Ridill from Norse myth. Kusanagi and the legendary blades of Masumune and Muramasa of Japan. Nandaka, the sword of Vishnu. Some of these weapons may not actually exist, or are mundane (albeit culturally sacred) blades. But it’s possible that such weapons contain strange energies that grant extranormal powers to their wielders.
Rings and Amulets: History, myth, and fable features all manner of rings, amulets, and talismans that when worn, are said to grant the wearer some kind of unexplained power. The Ring of Gyges, spoken of by Plato and considered the first “ring of invisibility” that inspired other myths. Draupnir and Andvarinaut of Norse myth. The various temporary charms and wards practiced by a myriad of cultures around the world.
Armor and Shields: There are a few suits of armor, pieces of armor such as helmets or bracers, as well as shields, that were considered magical in mythology. Hades’ Helm of Invisilibty. The Aegis, shield of Zeus. These items were not always protective in nature, and granted other specific powers, like invisibility or being able to swim as a fish and breath water.

Suggested Origins: My Legacy, My Mission, What I Carry, What I Know
Suggested Drives: Inspire, Lead, Protect

Example Characters: Excalibur, the Mandarin, Darkhawk, White Tiger

Mystical

Agents of STRIKE MattZenith MattZenith