Acantha and her kind are monsters whose purpose and origins are completely unknown. What IS known is that they are destined to become dangerous in due time–becoming enemies of the planet (and its guardians) by default.
But, rather than follow the monster hunters or the guardians, the narrative focuses more on the lives of the different ghosts and monsters who change–for better or worse—as they attempt to uncover the mystery behind their existence and either heal or run from past mistakes.