Demon (I of Newton)

Demons are demonic humanoids from Hell, who run an interdimensional soul broker company.

Biology
Externally, demons are mostly identical to Humans, with the exception of glowing white pupils on dark eyes and two white horns that protrude from their foreheads. However, demons are immortal, and have incredible reality-warping powers, able to make invisible forcefields, extract Human souls, and make two electrons occupy the same space with great ease. Additionally, demons are capable of moving much faster than the speed of light, capable of crossing galaxies in microseconds, can jump between dimensions and timelines, and possess nigh-omniscience, their minds being considerably more powerful than Human minds.

Culture and society
Demons, by their own admission, are evil, taking great pleasure in toying with and taking the souls of Humans. They function as soul brokers, using an interdimensional species-wide corporation to sell the souls they steal to various extradimensional beings rather than hold them in Hell. Whenever a demon is summoned by a mortal, accidentally or otherwise, they will take the soul of said mortal, but not before offering a chance to save themselves with a game of questions. They allow the victim to ask three questions, which the demons must answer, and then a fourth question, which could also be a command. If the demon is unable to complete the command or answer the question, the mortal's soul would be saved, and the demon would be violently pulled back to Hell, but as it is near-impossible to stump a demon, they mostly do it just to mock victims, and claim that their questions are really just a formality, as mortal souls are supposedly forfeit the moment a demon is summoned. Despite their inherently evil nature, demons are known to act at least somewhat politely and laid-back when dealing with mortals, and do not use force outside of creating forcefields to keep victims from escaping. It is unclear what they use the wealth they accumulate from selling souls for, or what sort of payment they demand. Demon clothing resembles contemporary Western clothing, and while capable of speaking fluent English, the demons' language is considerably more complex, with its phonetic structure resembling speaking out complex mathematical equations. Demons have not been seen utilizing any form of technology.

History
Demons have existed since ancient times, and formed a company of soul brokers, and would take the souls of Humans who summoned them one way or another. Sometime during the 5th Century BC, a demon approached a Human who summoned him to take the Human's soul, and the Human's questions involved trying to find limits to the demon's power. However, the Human's attempt failed, and their soul was taken. Despite that, sometime during the Peloponnesian War, the same demon encountered a Human who was able to best him with a question he couldn't answer or a command he couldn't carry out, saving the Human's soul.

In the 1980s, somewhere in the United States, a college professor named Sam accidentally summoned a demon, the same demon who was bested during the Peloponnesian War, after angrily exclaiming that he would sell his soul to solve a complicated equation, with said equation's phonetic structure resembling a demonic incantation. The demon used an invisible forcefield to keep Sam inside the classroom, and explained how Sam accidentally summoned him, and that his presence is only a formality. Sam attempted to protest, but the demon explained how his species were simply evil, and thus didn't care about fairness, also explaining the purpose of his company, mentioning an extradimensional warlord who used the souls sold to him by demons to power his undead army. The demon then gave Sam the usual three questions proposal, with Sam accidentally using up his first question by asking "really?" Sam then tried to ask the demon about limits to his abilities, but the demon responded that he could break all physical laws. Sam then noted that his next question would be a corollary to his first, prompting the demon to compliment him on his way with words, musing about selling Sam's soul to a world of sapient binary digits. Sam then asked if there was any place where the demon could go that would prevent him from returning, but the demon claimed that he could always return to Earth, as he could surpass lightspeed and hop dimensions, before expressing some disappointment in Sam, expecting more of him, such as asking to see alternate histories. With only his last question or command left, Sam gave the demon a command, ordering him to get lost. The demon quickly realized that by his own admission, he could never get lost, and was violently cast back to Hell, saving Sam's soul and leaving behind only his sunglasses, Sam noting that the demon was no help to him at all before returning to his equation.

Appearances

 * "I of Newton", by Joe Haldeman (1970)
 * The Twilight Zone, s01e12b "I of Newton" (1985)