the dark one

After the defeat of zorc, the strongest dark spirit in the monsters spirit world, and in order to make the world ready in case of similar events, the pharaoh Atem used the millennium tools power to create a link between the two worlds, as a result ,80% of the world population has a link with a monster spirit giving them the power of that spirit.

But what will happen when a 4 years old kid gets linked with the greatest evil humanity ever known?

Note: most of the powers are like Canon while the spell effect will be explained so you don't need to know yougioh to understand the story