On the Origin of Monsters
Ok. Let's chat about where your monsters come from . . . and why that is important, and what implications it has for worldbuilding and your game.
In a lot of fantasy, especially fantasy gaming, the origins of monsters are, at best, nebulous. 'Magic'. “Mad wizards'. There's nothing wrong with that . . . but defining more clearly what the origins of monsters are in your setting reaps a lot of story benefits. And a unified origin for a large number of them can help bring your setting together around a central theme, while also lending consistency and verisimilitude.
By way of example, Tolkien's Middle- Earth uses a few, fairly closely related, origins for its monsters. Some few are twisted Maiar, effectively demons, like the balrog of Moria, and Shelob, and frankly all the giant spiders of Mirkwood, descendants of Ungoliant. Not to mention Sauron himself. Many are functionally more earth bound demons, twisted from natural creatures or 'created' by Morgoth, the dark god of the setting. Examples include orcs, dragons, trolls, all made in mockery of good creatures, if not literally crafted from them: elves, great eagles, ents. Less creatures are created by Sauron or even Saruman, both Maiar), again usually by corrupting existing things: Ringwraiths, half-orcs, Uruk- Hai, fell beasts. And very few are 'nameless things' predating formal creation, born perhaps of the initial discord in the Music of the Ainur, provoked by Morgoth but not his creation or beholden to him, like perhaps the Watcher in the Water at the Gates of Moria, and maybe even Ungoliant and her brood. Or perhaps she mated with such things to spawn her brood.
As another example, all the monsters of the Wheel of Time were twisted from natural things by the power of the Dark One: directly, via simple proximal contagion in the Blight, or by his agents, the Forsaken. We have Trollocs, the Myrddraal, and the like. Even the Machin Shin, the black wind, is a result, direct or indirect, of the taint on saidin placed there by the Dark One.
As an example of how to use these principles in your own building, we'll talk about the Successor States of Rega. I was inspired by both of the above, in some ways . . . but even more by human mythology. So before the dawn of time I have truly primordial things swimming through the void. Only one is named, Invidia, the original dragon, eating gods before they can wake up. She gets killed by the first god who does wake up, and her blood spawns monsters forever , twisting things around it...but also the dark gods are born directly from her flesh, and craft more monsters (dragons especially) from what is left, so that nearly all monsters come directly from her. A few are created later by mad wizards of course . . . but I know who they are, and the power used to do it is often based on her blood, or invoking her children.
In Greek myth, most monsters are children of primordial deities, spawned from the very same progenitors that gave rise to the Titans and then the gods. All Giants, for instance, are the children of Gaia. Other monstrous parents are Phorcys and Ceto, or Typhon ( son of Gaia and Tarterus, or Earth and the closest thing the Greeks had to Hell) and Echidna (child of the aforementioned Phorcys and Ceto, children of Pontus by Gaia, so of the Sea by the Earth), so one sees that in the long run almost all monsters are the product of the Earth itself. Medusa is one good example, originally born a monster, a child of Phorcys and Ceto, granddaughter of Gaia.
Honestly, even my Alternate Ecology series sort of embraces this idea, as it develops. Most monsters, as I examine them, seem to come from the primordial Khaos. Some come later, from the slightly less chaotic elements, but still primal. I'll get into that when I start talking giants. But as usual, I digress.
The point of all this is how to use it, and why it matters. If you don't know where your monsters come from, all you have is a thing to fight. If you know whence they come...you have lore. You have mysteries. You have relationships, connections...the monsters are truly part of your setting. You may even know their motivations for monstrousness. Because, yeah, even monsters can have motives. They aren't really reserved for villains. Typhon and all his spawn are basically driven by the anger of Gaia at her deific children for their mistreatment of her other children, the giants. He himself is driven by ambition. He wished to wrest control of the cosmos from Zeus . . . but it was still part of Gaia's revenge.
Likewise, in Middle-Earth, the motivations of most monsters go back to their creator. Dragons are greedy and destructive because Morgoth made them that way, to use as living siege weapons against the Valar, the elves, and their allies. Even when they don't directly serve Morgoth or his lieutenant and successor Sauron, they serve his purposes by opposing and distracting his enemies.
The monsters of the Wheel of Time are the same way, acting as servants of the Dark One and his emissaries the Forsaken, or guarding ways to get to him like the monsters of the Blight or even the Machin Shin. And so, it is the same in Rega. So many monsters exist because of the intent of the Dark Three, and even more because of the intent of Invidia, which is destruction of all and opposition to the Bright Gods, and even those just changed by her blood are driven by her urges: envy foremost , but all the deadly sins of Catholic tradition. The taint in her blood and her flesh carries tiny bits of her will.
This unified origin and mostly unified purpose even amongst widely disparate creatures allows for focused themes and moods, which feel more real and intense than just random evils scattered around creation with nothing in common.
And even if they aren't singular and unified . . . monsters are better when they exist for a reason. When something gave them a purpose, a drive. In the case of more natural seeming creatures, that purpose can just be the purpose of all life: survive. But then, if that's their purpose, no matter how horrific they may be, they aren't really monsters. They are creatures, animals, just living things, no matter how weird. Because monster actually means something pretty specific, at least in its origins.
The word monster has its origins in the latin word monere which means warning. This developed into monstrum, meaning portent or monster, then later into monster in English. Monsters are warning signs, indicators of something very wrong going on in the world, something worse than them, often the rise of more intense evils. They were always characterized by being unnatural, with unnatural urges as well.
So things like owlbears, despite being what seems like an unnatural amalgam to us, if they act like a normal species, concerned mainly with hunting and having and raising their young . . . they aren't really a monster. They are more like a fantastical element of the ecology. And even there, you need to know their origins and inclinations, so you know where they fit that ecology!
So, basically, knowing where things come from helps you understand where they fit into the world . . . which helps you see how to use them in your campaign or your story.