Shackled magic

A magic world that is home to only one kingdom, which is ruled behind the scenes by 10 different immortals, some good, some bad. When necessary the 10 immortals meet together to stop any others, who are not them from getting too strong, to do that they secretly imprisoned all of those with high potential, while letting decently high ranked people look like heros, or villains, they test the true talents behind the scenes making them stronger, but with a drawback, by changing their cells to see how the evolution process reacts, to find the best abilities, and how to get around the downsides. Basically the people who can be strong enough to destroy the world, or protect it, are put together and used as lab rats for power, but only the strongest of the strong so no one would get suspicious. But this world is one of two known as the human world, the other is known as the monster world, this one is much more primitive, around the point where they have tribes of monsters with a leader of a territory yet, they are stronger individually than humans, there is only one way to travel between the worlds known as portals, originally it was made by monsters by inverting their energy, which comes more naturally to monsters, making it so they enter a pocket like dimension, between the worlds while their energy adjusts, which takes 24 hours, in that time a portal is visible from both worlds, but the inside of the portal isn't, only the world being invaded can enter the portal, only enough so the energy from both sides are equal, if the monster of that portal dies the portal does not dissappear, instead the human can choose which world to go to, and, they can choose if the portal gets destroyed after, sometimes the humans choose to keep the portal, so they can go between worlds, but most prisoners of the 10 immortals do normal portals with technology hooked up to the portal forcing the prisoner back, and if you some how get past that then they send a specialized team to either kill you, or get you back.