LOST TWIN souls
yield to one
Most mortals in all planes of existence have two souls, which through their waking lives vie bitterly for dominance, hand over hand, in an endless struggle for control. But when death befalls the mortal, these souls drift apart, and soon realize their need for each other. Some souls remain bound to their native plane from unrealized requirement, while others wander aimlessly through dimensions and time, seeking their twin soul.
As these souls remain apart, they become restless, and devolve through such disquieted states that they take on new forms of mischief and power. These transformed beings become bent only on gathering any souls that they can find for power. These invisible spirits go by many names, but we call them the Yokai.
As Yokai collect what souls they can find, they grow stronger, and develop mastery over elemental forces of magic based on the dispositions of the souls they capture. And often, knowing that other Yokai may have their partner soul in captivity, they engage in battle, with the slim hope that they may end their journey, and reunite with their twin soul to become one whole, a being known as a Yokaizo.
…
But not all mortals are born with two souls—some have only one. These are known among the Yokai as Summoners, as all Yokai are drawn to them, and their power does not wane in death, but flourishes. The Summoners gather Yokai like families, and help them on their journeys to find their twin souls.
One day, you are approached by a Yokai which recognizes you as a Summoner. That Yokai asks you to help them on their journey, and you accept. Now, you prepare for battle against another Summoner, both of you wishing to serve your legions of Yokai by unseating your opponent’s souls, in the hopes that at least one of your Yokai can become a Yokaizo.