After transmigrating, Roy awakened the Mangekyo Sharingan as his golden finger.
It gave him an almost BUG-level set of abilities: invincible intangibility, spatial teleportation, and storage in a pocket dimension.
But using these powers came at a price. Unlike in Naruto, where they were sustained by ocular power, the Mangekyo Sharingan’s fatal flaw in the world of One Piece was that using its abilities caused his eyesight to deteriorate rapidly and irreversibly.
So, to keep from going blind, Roy pinned his hopes on a Devil Fruit that could completely eliminate the side effect: the Paw-Paw Fruit.
And that fruit was in the hands of the World Government.
To get it, Roy joined the Rocks Pirates of his own accord. With overwhelming strength, he quickly became a monster on par with Kaido.
When Rocks cleaved the sky with a single sword stroke and led the strongest pirate fleet in history toward God Valley, Roy had only one target in sight:
Steal the Paw-Paw Fruit before Kuma!
Once he succeeded, his goal was achieved.
The Mangekyo Sharingan plus the Paw-Paw Fruit: that was true invincibility.
Intangibility made him immune to physical attacks, and he could slap away fatigue and pain, never knowing exhaustion...
So at God Valley, Roy kidnapped Celestial Dragons, recruited Kuma, Ginny, and Ivankov, and claimed every Devil Fruit for himself.
Thus, a tyrant of the world was born.
Starting at God Valley, a true King of the World began his journey.
