Cain stared at the Devil before him with a calm face, his thoughts unknown...
The Half-god grade was something hard to understand...
Every creature, great and small, magical and mundane, could be graded based on their potential. While he wasn't exactly sure how many grades existed, Cain was sure the Half-god Grade was relatively high on the totem pole.
Gods and Celestials, are quite different, in a sense that all Celestials are gods, while not all gods are Celestials.
A strange paradox, but a valid one...
A god is a creature with dominion over a concept, element, material, or even people...
All Celestials can be gods because of their limitless potential, but it is very possible for a regular creature, other than a Celestial to attain godhood. It was just very, very difficult.
A creature, with the potential to achieve Half-god state, was one that couldn't be trifled with, even on a good day.