When Alex got his void core, it appeared colourless under his divine sense and although small, in his perception, it was sufficiently large.
He could 'see' the minute fluctuations it gave and how it produced a golden light whenever he used his light abilities.
His theory was that the core and his void energy were intertwined as it was that energy that powered his skills and the mana in his body cells.
As Alex began to absorption process, he 'watched' the void energy carrying the same hues as the blood and flames of the void creature.
It entered his body and into his energy channels as the core drew upon the energies. It seeped right into the vortex and disappeared into its abyss.
Alex felt no different than just absorbing void energy, but even if nothing occurred, there was no point in harnessing the void energy.
