This is Takuya. He resides within that small orb within the center of the Traveler's Keytool.

In essence, without going into the long and involving description of his past and creation, he is an artificial biological entity of extraordinary power that is capable of growing infinitely stronger and more intelligent by assimilating data from everything it comes into contact with.

Or even more simply put, The Single Most Dangerous Entity in Existence.

So long as it remains sealed within its tiny spherical prison, it is locked in slumber and virtually harmless, but once released, Takuya will awaken and unleash his fury upon whatever foe is placed before him.