Gains [1]
There were two main things that Damien knew he had to focus on when it came to the gains he made. The first was his golden flames, and the second was the dark material he devoured.
As far as he was concerned, there weren't any other gains he made, but he had to check on his own body to be certain. He didn't end up devouring Polius after he died either.
There was a simple reason for this. In that final moment when the dark material was desperately resisting his Seven Stars Encircle The Moon attack, it had sucked Polius dry of all his vitality and experience, making his corpse completely useless even if devoured.
The first thing Damien did when he sent his awareness into his body was attempt to locate his flames.
When he summoned lightning, he usually just transmuted his pure mana into lightning mana to produce his black lightning. After all, besides its color, there wasn't anything special about it.