Oblige
Leonel lived up to his word. His brothers couldn't even believe the kind of strength that was coursing through their veins. But it wasn't as simple as that.
Leonel didn't even particularly add to them; it was as though he had framed their potential and made them see just how much of it they had locked away within them, only limited by their upbringing and lingering issues that had remained from their youth.
There were three major things each one of them gained when they fused with the Incomplete World.
The first was a new foundation. Leonel didn't add to their strength; he used [Assimilate] to refine their foundations, forcing them to unearth their fullest potential.
With [Assimilate] and [Dimensional Cleanse] as a foundation, he basically reforged everything that they had already accomplished on their own, improving it.
As such, they felt like barely anything had changed, and yet like everything had changed.