This is an infinite stratos idea
we a know how the IS literally changed the infinite stratos universe. But what if there were other powerful weapons that could match the IS and has the potential to destroy the world that existed long before the IS
Here's my idea
in the height of the industrial Revolution . A group of scientist , scholars ,bankers and philosophers created an institution called Renevant. Renevant was institution or some kind of college that was stationed Austria.It looks like any ordinary college but had dark secret. Its members were obsessed with creating live , bringing the dead back to life , controlling plagues , discovering new energy sources and creating powerful weapons of mass destruction. They started experimenting with corpse and living humans who were kidnapped. It's experiment were inhuman and cruel . Renavant was run by basically madmen . They discovered new energy sources. They began to theorize to create various kinds of deadly weapons . The people who ran Renevant knew basically they were gonna get screwed if someone finds out what they were up too. In case if everything went downhill. They started to construct a city deep underground in the Alps. To help the city built faster . They constructed machines out of the new energy sources they discovered . Eventually word got out and the Austrians send an army to eliminate them. When they arrive the entire College was destroyed and no one was presented. Evrything in the college was gone . Meanwhile the Renevant was able to complete the city and called it Juttreheim . But the city lacked 'residents'. Renevant began kidnapping people to populate the city . Juttreheim was well modern for its time and had machines. But the Renevant continue to experiment with the people and turning into a sick social experiment. The people changed widely. Renevant accidentally 3 kinds of subhumans. There were the normal people.
1Beastkin people with animal appendages. They were changed because Renevant experiment on them using animal blood, DNA and genes. They have animal senses also
2 Auserwählten or chosen ones. These people have strength and senses because of the inhuman experiments.
3 Unheilig. Unheilig or unholy were people who suffered much more worse of the inhuman experiments. They have horrific deformities, they can't talk so good, and their appearance's are of corpses other looks like unspeakable horrors .But they are most powerful of all three subhumans
Renevant began creating weapons powerful weapons.One of which was a mecha suit similar to an IS called Valkryie . But are very different. The Valkyrie uses a dark matter reactor which can be quite unstable if not checked on time or stored properly. and it can be use by males . Another is 'Golem' . Sentient machines with the potential to do various tasks. (You can add your own weapons also because I am lazy to think of more )Renevant also created 3 mysterious project. 1 was Raganok. rumored to be a virus carrying disease that could ravaged humanity to its knees and could cause an epidemic. 2 Wrath of God . During the height of the cold war Renevant came to the world but stayed hidden but for a goal . It convinced the US to 'launch a satellite for civilian purpose. Only problem was this was a orbital space canon which can destroy cities and rumored to cause earthquakes and tsunami. 3 Apocalypse. The most mysterious. Nothing is Know of this but only a few knew this was plan to create a black hole and destroy earth itself. Renevant also had other idea to conquer the earth but there was a massive uprising all across Juttreheim. Renevant was overthrown and all of its members were killed in revenge. Juttreheim became an hellhole . Renevant was the only thing keeping it stable. The city became pretty political unstable and there's was a civil war . The civil war ended and Juttreheim was somehow able to become stable but was in horrible condition. they open themselves to the outside world. A lot of people were schoked. in attempt to keep up with the world and hearing about the IS and wants to learn more .They sent a girl (Which subhumans you want ) to the IS academy and acts as their representative. She meets Ichika and his harem and forms a friendship. Unfortunately Phantom task decided the girl to be a priority or a threat.