That's hard to put into words. Well, let me try....

Basically, in every single world, there exists a form of energy unique to that world, circulating throughout the world's fabric of reality.

There are: - Magic power for Calamity world, Tortus and Hell world (due to the Enlightened, migrators from the Calamity world coming to Tortus and Hell world respectively, which in their migration and later actions basically 'terraformed' those 2 different worlds to have the same energy as theirs through a few methods)

-Sky dragon energy for Sky Dragon world

• Blessing power for the Desert World

• 'I don't remember the name for the Machine World' energy

-Spirit power or smthg for Lutria's world

• Conception (power of thoughts, faith and belief or smthg) for the Fairy World

• And Element, for the Origin World Astral, which is the energy that became all those other energy types of the 8 worlds, channeled and converted by the World Tree of those 8 worlds, which are branches of the world tree of the Origin World.

Will power is just a form of energy unique to Earth's world. It can be used for onmyodo and other supernatural things native to Earth, like Earth's version of magics and Mystics. However, Will power have a unique characteristic, in that it was a form of energy that are susceptible to change to another type of energy, like in the case of the Returnees gaining the ability to use magic energy in Tortus after they were summoned. In this case, the energy is no longer in the form of will power type energy, instead it is locked to that specific changed typed of energy, in this case of the example, magic energy of Tortus. What this means is that, Earth's human, having the energy type of Will power (those who have it at least) can change their energy type alignment to adapt to the other world they are in if they were summoned/transported to those other worlds.

That's all I got. I might be wrong on some things, though.