All the World-Termination-Armour were created from the bones of the Demon King. Even though it could bring them huge power, but the damage to the human body from the remains of the Demon King could not be prevented.
Just when all the kingdoms were at their wits' end, the people who had sent the world-termination-armour appeared once again. This time, they gave all the kingdoms a solution.
The only ones who could withstand the damage of the demon aura were the demons themselves.
But it was impossible for the demons to fight for the humans.
So…
There were the current terminators.
A group of mutants who were produced from humans and demons.
The people who sent the World-Termination-Armour specially picked a group of people from the noble families in all the kingdoms. Making use of their bloodline, they gave birth to a new race with the high-level demons that were captured—the terminators.