There was a difference between monsters and beasts.
Monsters were sent from hell and resemble humans, while beasts were naturally occurring and sometimes influenced by magic.
Where they were the same was their desire to slash down humans and cause chaos. There wasn't a reason for their actions other than the survival of their own.
This brought up the fact that goblins were the lowest classification of monster that the world had ever seen.
Mindless creatures that only knew how to fight, steal, and procreate. There was much debate on whether or not they even had a brain behind their eyes or a heart in their chest. Those with enough curiosity explored the mindless theory, performing dissections that led them to a mess of organs unrecognizable by humans.
Their dark insides, along with nearly black blood, made anything inside of them indecipherable. The conclusion was mostly that they had small minds and hearts that wouldn't lend much to them in terms of anything beyond living.