Demons were a race of creatures that brought a great headache to the rest of the races.
Their vile ways of doing things along with their carefree nature was something many disliked. Add to that, they openly did everything to fulfil their desires.
Demons were supposedly one of the strongest races as per the Grand Lust Sovereign's inheritance and weren't to be trifled with.
It was exactly due to how extreme their cases were that other creatures who may have strayed from their normal moral paths were termed as demonic.
Lith didn't exactly know if this world was going to be hit with a Demon invasion, but he did have some rough clues to such a thing happening.
People wouldn't disappear for no reason so suddenly as Demons weren't so dumb to give out hints openly.
If they had started acting now, then this meant their plans had begun and it wouldn't be too long until a full scale war.