The backstory for Underground borrowed heavily from Pat Mills' Marshal Law and Alan Moore's version of Marvelman, two of the earliest deconstructionist superhero comics of the 1980s.

The art used in Underground was intentionally inspired by the Aeon Flux animated shorts, as well as the comic books Marshal Law, Watchmen and Elektra: Assassin!.

The UFO was a small escape pod from a larger interstellar starship and contained a pair of lobster-like aliens, codenamed Alpha and Omega.

Apparently, the alien technology was based entirely on manipulation of amino acid chains and advanced biotechnology, which started a revolution in genetic engineering.

This causes them to have an underdeveloped pre-frontal cortex, so they have an extremely low intelligence, have difficulty delaying gratification or forming long-term plans, and have trouble separating fantasy from reality.

They exist as a servant class that is deprived of all civil rights due to society legally and constitutionally redefining what it means to be "human".

These were concentrated in urban sprawl areas of large cities on the west coast so the veterans could be segregated and easily controlled, making Los Angeles home to the largest "boosted" population in North America.

Large multi-national corporations can legally enter into treaties, grant diplomatic immunity, and field private armies (which they typically rent out to other entities).

The most popular fast-food chain in the world is Tastee Ghoul, which exclusively serves human flesh and gives away disposable polymer handguns in its Happy Meals.

Then after being decanted they work as augmented mercenaries (called "Boosts") for any one of several private armies operated by giant corporations, fighting in small wars around the world.

This is paired with psychological conditioning (the Bushmiller Process) in the form of a virtual reality simulation (called "Dreamland") that teaches them how to handle and use their new powers.

The virtual world looks just like a "four-color" Silver Age superhero comic book, except it's ultra-violent and merciless to simulate combat conditions and desensitize the recruits to violence.

A Player Character begins as he's discharged from service as a genetically enhanced warrior who had been conditioned to think of himself as an ultraviolent superhero with a bizarre origin story and a dramatic past.

They tend to see the world in the uncompromising black-and-white ethos of superhero comics filtered through the mental illnesses and phobias triggered by the process that grants them their powers.

It is presumed that the player characters join and form various "Underground" movements to oppose the government, giant corporations, or other tyrannical forces in the world.

Robin Jenkins (1993) Hell Bent was published by Atlas Games AG5400 isbn 978-1-56905-063-7 Chris W. McCubbin reviewed Underground for Pyramid #2 (July/Aug., 1993) and stated that "Any super hero GM with a nasty sense of humor (and in my experience, that's most of them) is advised to buy this book for the excellent background material.

Off the top, about a third of Underground hits sour notes, born largely out of the conflations of shock value with the perception of maturity and a conscious desire to cut against the omnipresent notion of political correctness, a very '90s era pitfall."

Horvath concluded, "For all of the poor taste, wobbly satire, and ultraviolence in Underground, I can't think of another RPG with a system so explicitly focused on making the world a better place, one block at a time.