A world where the inhabitants each have certain powers contained in their soul. This power can only be harnessed if a person has been gifted with a special gateway, which grants their soul access to the outside world, and allows them to utilize it as a weapon, tool, etc. Whoever controls someone's gateway controls their soul's power, and by default, them as well. If someone dies while in possession of their own gateway, their soul passes as well, but if the gateway is in another’s ownership, the soul remains trapped in the gateway until it is returned to the deceased owner. This means that the soul's power can still be used, even if the owner is dead, by anyone who holds the gateway. However, it is possible, through a complicated procedure, to reunite a soul with a body, restoring consciousness and a sort of life to the deceased, as long as the death was not from loss of blood, and the body has been preserved with all organs.
Not everyone has their own gateway, because the gate chooses the person, and then shows them how to wield their power. How someone is chosen is still unknown, because not everyone appears qualified to hold so much power; for instance, those of a criminal bent. This does not matter too much normally, because everything seems to sort out in the end, but once, a villain rose up, far more powerful than anything seen before, and they thought no one could stop her.