So basically it's like a dragon ( or other monsters turn into a mech with like bio mechanical parts ( as in biomechanical I mean like literally the Mecj is made out of Bones veins nerves blood vessels things like that) but in order to activate it there are specific requirements for specific Mechs and how powerful it is, for the first version is obviously just a standard monster soul and it is bounded to it kind of like a symbiotic relationship where every time the Mech feels pain you do as well, because the monster soul gives it life and uses the nonsters blood as well as fuel. And if it gets destroyed then you as the pilot dies. The second nost powerful require you to input a HUMAN soul to fuel it as the human is bounded to it. And for the 3rd strongest its a boss monster and a human soul. And 4th is the most strongest ever recorded in history made by 7 human sorcerers. And 7 boss monsters souls.