But this isn't very practical in real life.
Because he didn't have an "Instance Finder" to randomly arrange instances, and Phantom Demons couldn't infinitely respawn like the bosses in the instances. So he could only feed them corresponding rare materials to level up the Phantom Demon—which required a huge cost, and collecting materials also took time and energy.
But if he had the "Shepherd's Nurturing" skill, he could use himself as fodder, sacrificing to the Phantom Demon.
Aiwass's oath was "I will not use the lives or corpses of my own kind as ritual materials or offerings," and he certainly didn't fall under that category.
After all, "self-sacrifice" was a standard ability for Demon Scholars. Moreover, it wouldn't prevent advancement to become a Great Sin Scholar.
Though "Shepherds" would become emaciated and scarred due to this flesh nurturing.
