I’m having a hard time drawing a line between the regular races of the world I’m creating and the Monsters/Beasts with intelligence. Example- Kroblins: They run around on their hind legs. Surprisingly agile. They drool a lot. They like to steal things. They use the things they steal. Like to wear human armor and use human weapons. Good teamwork but kinda dumb. They move in packs. (Green furred wolf monsters, slightly human like bodies.) This a monster of my world but here is a regular race. Example- Mashies: Types of mushroom people. They have very short life spans, some living only for a year, others five years at most. They eat dead things. • They live solitary short lives. • They like water fairies a lot and dislike fire fairies. (Different types of mushroom, always have a mushroom cap on head. Different colors and effects on people. Gender neutral.) What can I do to separate them?
How about using beast(s)/monster(s) for regular races and magic beast/ demon beast for intelligent monsters. Hope it helps.
I saw this meme on a DnD forum once. "Can it consent to snu snu? Yes? It's a sentient being. No? It's a beast." XD As for weather they are "monsters" that's more of a political question. Take for instance a human and a vampire. The vampire is seen as a monster because it hunts and eats humans as an obligate hemovore. But in a society of vampires, a human vampire hunter may be seen as a monster since it's something that should be prey but hunts them instead. Like imagine a killer rabbit or a man-eating cow. It's all about perspective.
Traits such as emotion, empathy, morality, metacognition, or ability to recognize/respect the lives of other species are some innate ones. This could lead to a psychopath being classified as a monster and treated as some kind changeling or doppelganger. Free will is a bit trickier to demonstrate but monsters could be behaviorally mechanical, ruled by instinct, or puppeted by an overmind. Otherwise what can divide "monsters" and people will come from the world they are in. A devout set of races might use capacity for faith or biblical origin to define monsters. More pragmatic races usually base it on who can be cooperated with and who is hostile(or inconvenient).
1. consider why you want to separate them and whether you really need to separate them. because what people define as monster or race could just be a difference in opinion/perspective - for example: the general masses/peasants may define anything non-human as monsters, but knights/guards define anything that is inherently a threat to humans as monsters, but mages/scholars define everything as different races. 2. monsters are often different from animals in that they instinctively prioritize attacking humans/human races over self-preservation, - so for your kroblin example - they would use tricks to steal better, but do not even think about retreating monsters often also have demonic/mana core (unlike regular animals) that people like adventurers can harvest I also agree with Villager anonymous 's comment about emotion, empathy, morality.....
I agree with all the advice you've gotten so far, but to give my own advice is that you must create a reason for a monster to be a monster and a race to be a race. What I mean by that is many novels differentiate monsters through mainly three types 1. Intention - Destroy the world, work for some evil god or demon, etc. 2. Energy - They have a distinct energy that categorizes them as a monster (core, mana, etc). 3. Threat - Destroying villages, killing humans/other races, etc. If you don't have these figured out, it would definitely be hard to differentiate Kroblins from Mashies, especially when considering the different perspectives your own characters would have on them. I agree with JIKI that you don't need to separate them and can just throw them under the label of a race as, to be fair, you can say monster race or Kroblin race as well and say they're a threat or something similar. If that doesn't work for a narrative reasoning, you could probably have each main race excel at one thing (The common troupes of Elves are good at spirit magic, Dwarves are good at smithing, or even Mashies are great herbalists) while also having prosperous communities and are able to communicate with each race. You should also be able to get away with just "races are able to be peaceful while monsters are violent".
If you want to add the potential for multiples viewpoints in your world you can go for the hypocritical point of view of "all the "races" view them as "monsters" because they attack or bring a lot of trouble for people systematically" while they don't consider warmongers, bandits and other criminals of the "races" as "monsters", which would allow you to play on the "who are the real monsters", or even make some side story for the POV of an intelligent monster hunted by the "races" for the sole reason that it is a "monster" for them, adding shades and layers to your world building. And if you want to go for something simple but with some potential if you want to have some moral leeway in your narrative Evil Vs Good stuff, you can use the "VOICE" template (where monsters hear the "VOICE", maybe some ancient echo of a fallen deity screaming for revenge and murder on the "races" while the "races" can't hear it but know its existence thanks to some intelligent monsters that tried to resist the "VOICE" but ultimately failed) to explain the "monster/races" separation... I used it in one of my tabletop rpg game campaign and it was quite efficient (and you can play on the "DO YOU HEAR THE "VOICE" ?" for some nice tension spike or a radical world view reversing...)
What I want to ask is what exactly do you mean by "separate"? Do they live in the same place? Do they look the same? Do they behave the same? Shouldn't it be clear which one is which? How do you measure intelligence in your novel? These Kroblins seem to be somewhat intelligent, so how exactly are they different from the mushroom people, other than the species? Do mushroom people not have a civilization or a society? Or is your question is actually more fundamental, exactly about this? Normally we would define intelligence by ability to communicate and also by having such things as tools and some form of society. If neither of your races can be distinguished from each other by these means, are they actually separate? So if you want to draw a clear line, I would go towards two things: the behavioral patterns and a form of society they have. Maybe make your monsters dumber on average and only make some of them who are something like a leader smarter. Not all of them would be able to use tools and wear armor, for example.