The monolithic "enemies" of the Shadowrun world (borrowing heavily from cyberpunk mythos) are the corporations, dubbed "megacorporations", "megacorps", or simply "megas" or "corps" for short. Megacorporations in the twenty-first century are global, with all but the smallest corps owning multiple subsidiaries and divisions around the world. They are the superpowers of the Shadowrun universe, with the largest corporations having far more political, economic, and military power than even the most powerful nation-states.
In Shadowrun, corporations are effectively "ranked" by the amount of assets under their control, including material, personnel, and property, as well as profit. These ranks are A, AA, and AAA; AAA corporations are top tier. Most corporations in the AA and AAA level are immune to domestic law, responsible only to themselves, and regulated only by the Corporate Court, an assembly of the ten AAA-rated corporations.
All AAA-rated and most AA-rated corporations exhibit a privilege known as “extraterritoriality”, meaning that any land owned by the corp is sovereign territory only to the corp and immune to any laws of the country within. Corporate territory is not foreign soil but corporate soil, just like its employees are corporate citizens, though dual citizenship in a corporation and a nation is common.
The AAA corps, as well as numerous minor corporations, fight each other not only in the boardroom or during high-level business negotiations but also with physical destruction, clandestine operations, hostile extraction or elimination of vital personnel, and other means of sabotage. Because no corporation wants to be held liable for damages, it has to be done by deniable assets, or shadowrunners, invisible to the system where every citizen is tagged with a System Identification Number (SIN).
Shadowrunners fall outside the structured corporate world. Many are outcasts, having risen from the streets or fallen from corporate or government ranks. Their ranks include idealists and pragmatists, professionals and amateurs, disillusioned ex-corp/government/military personnel who have thrown off the shackles of corp society to achieve freedom and those who have never known any life outside the shadows. The one thing they have in common is that through necessity or by choice, they work in the shadows cast by the gigantic corporate buildings. Players of Shadowrun most commonly assume the role of these shadowrunners.