Summoners of Humans - An Epic Tale of IdiocySetting: The Underworld. A place composed of several layers of Hell, with the demons living in the innermost layer. In ancient times, when the men still wore armors and wielded weapons made of bronze, Terra and Hell colided. It was an unsung war, a conflict of continued and bloody combat from both sides, where the might and muscles of common knights and the wizardy of terran mages confronted the giant figures of twisted demons and the sorcerous powers of devious archdemons.
Ultimately, the Devil was slain, the forces of evil were defeated and forced back into their own plane of existence, banned from the realm of humans after both sides sustained heavy casualties. The biggest loss, however, was that of the demons. The humans mourned their dead but commemorated the victory over the denizens of Hell. The evil beings, on the other side, lashed out in anger and cried in despair as the fact they had been defeated humans hit them. That would not stand forever.
Fast forward some centuries after that, when the war was naught but a far and dim remembrance from the past for the demons, having been mostly forgot by the humans. Summoning and tending to creatures from the outer circles of Hell is an usualy practice of the demons, for these beasts are used as mounts and war animals. Hell has been slowly but steadily regaining its military power and preparing its forces for a new attack on Terra. But this time due to improvements to the summoning system researched and implemented by the new Supreme Lord of Hell (the second Devil), victory would be complete and certain. The Terrans had developed new weapons and tactics, but they would not stand against the might of the voracious and hellish creatures. The Devil was respected by the demons and all of them paid fealty to him as the one who kept Hell as a cohese, effective unit.
During an experiment the Devil poured enormous amount of energy into a portal and accidentally summoned a human wizard. The magus was dressed in common clothing and masterfully hid his magical presence as soon as he felt being punted into a different realm, but as he was pulled into Hell he left a node to transfer part of the energy contained within his own Tower to him through the open portal, the technique being one of his experiments. The Supreme Lord thought about the idea of keeping the man as a pet and voiced his wish out loud. The wizard simply turned his back on the Lord and would head home if it had not been for the Devil, who pulled him back, promising him pain and suffering for all eternity, even though the demon himself had probably discovered the peasant's true nature already. The demon lord's retainers at first were aprehensive, but then remembered the man who was summoned had no armor nor robes, and lacking their leader's superior detection abilities, concluded the human was probably a harmless commoner. As the wizard finally sighed and decided to play the Devil's game, they discovered they would come to regret the failed attempt at summoning.
The Wizard fought against the Archlord using only physical attacks boosted by magical energy. The Devil and the magus tore the castle asunder in their fight for days, and the ridiculous scene of a rag-wearing peasant fighting against the Devil Lord, who in turn was clad in a lavish full-plate of gigantic proportions, was seen by most of the demon world. After dozens of hours of heated combat, the human finally pierced the armor plates with his bare fists in several areas and proceeded to tear off the demon's curved horns from his head, finally crushing the Devil with his own mace before disappearing into the portal.
Needless to say, Hell was in turmoil. Following that event, some of the more powerful retainers of the dead Devil attempted to summon humans themselves to prove some of them were harmless...Right? Due to a combination of both bad luck and excess of power inputed into the portals, the magical systems outright refused to bring any weak human. The demons were oblivious to that failure in the summoning ritual due to the fact it had been developed and taught to them with a series of preparations by a mind which worked at a higher level: their former master. That made the ritual almost impossible to be analyzed and any flaws to be discovered and corrected. Consequently, the retainers kept summoning extremely strong warriors and wizards, who sometimes were less than happy to be summoned from their home while they were brushing their hair or eating breakfast. The demons finally gave up on all of the stupidity when they finally summoned a very old human - who happened to be a retired badass. After the old lady finished moping the ground with two former elite guardians of the castle and got back to Earth to feed her cat, Mr. Fluffy (probably not even a cat), the remaining members of the Council of the Lord sealed the portal link and forbid the summoning of any humans. That was then....
...This is now. A couple of centuries after the death of the Devil and as the lands were left without a strong, centralized government, the demon realm has been divided in several warring reigns, much like the human world. As the humans, they also have an arms race happening, with each minor Lord attempting to dominate the others and become the Devil of the Underworld. Most of the demons even seem "humanized" up to a point in their visages. Even though most still have an alternate form which is shaped as the devils of old, most the younger demons are humanoids, although no one knows why, and although their lifespan is long, none of the demons from the "War of Origin" still lives, most having been slaughtered during the "Second Coming".
Due to the information amassed during their last contact with the humans and that has been distorted over the ages, the demonkind believes humanity to be a race of wicked beings from a plane where every single person is a living God and even looking them in the eyes could lead to certain death. Some shrines to "human Gods" exist, especially for the "peasant" who killed their second leader. Humans are eldritch abominations of infinite power and rage, and no sane demon would dare try and open the seal once more, but desperate times lead to desperate measures. One of the demon kingdoms has tinkered with the bridge between both worlds until they were able to make it work once again. Then a taskforce of demons - preferentially the younger ones, who do not need to shapeshift in order to appear more humane - was assembled to summon humans and finally win the war. The deterioration of the portal was actually able to fix what the demons were never able to: unbeknownst to the summoners, the portal is now able to suck weak humans into Hell.
TL;DR version: Demons fight in the Underworld and think each and every human is a being in the same level as Cthulhu. They summon humans (the PCs) to help them in their wars while being terribly scared of them. Hilarity ensues.
So, what the hell do I want with this anime-esque shit (I hope this was not yet used in an anime or manga :V), you ask? Comic effect and developement of powers, of course. The demon taskforce would also be composed of player-controlled characters, but I was considering two options:
-The human PCs are common fantasy adventurers, but they are just newbies. Like your classic weakling mage/thief/warrior/knight ensemble.
-The human PCs are everyday modern young people. Like you and me.
Of course, the result would be the same: They would be flung into the demon realm (fantasy!) and would be covered with promises of wealth and power and anything they ever wanted if they just accepted wearing that armor, carrying that banner and destroying everything in their path.
That would not work for obvious reasons, because the human PCs are at best talentless slobs and would have to learn something while on the Underworld to try and live up to the human race's image.
The demon PCs would have to act like the rest of the demons: thinking all humans are Lovecraftian horrors which must be held withing several layers of armor so your eyeballs are not exploded due to excess of exposure to their tainted flesh.
Of course, the initial weakness of the humans would be quickly explained by the demons (and quickly accepted by the eager humans) as summoning sickness and then further explained by the loss of most of their abilities due to a faulty summoning ritual, but the human ensemble would have to get enough experience and fast enough to fare at least reasonably against the enemies who didn't run away from them. The main problem I found is that it requires too much RP, so here I am trying to find a way of simplying it. Turning the Demon Taskforce into NPCs is the most feasible option so far, since demon PCs would discover things too soon due to meta.
Note: It was created right now on the fly, don't hate on me.
Also, if any media has already used the same idea, poke me so I may frown and give up on it.