At the outset of Wolves, I made the decision to limit myself to only using recurring monsters from Volume 2: Monsters &. Whilst there are the occasional unique creatures, the vast majority of monsters are taken from it.
For those not familiar, V2M& is a rewrite of a select few monsters from OD&D Volume 2: Monsters & Magic - a selection of which can be read using the MMM tag on this blog.
This restriction has added to to the cohesive feeling of Wolves - rather than being able to simply invent creatures, or select a novel one from a larger collection, the use and re-use required me to think deeply about each type of creature. The differences in each instance stem from the situation they are in - these situations being an outcropping of both the setting and the implied history and nature of each creature specifically. Furthermore, the placement of such beings across the world adds to their context, something visible as the writer, as the GM and as the player over recurring encounters. Whilst this method requires more thought in placement and presentation, I think limiting your palette of monsters can have a very positive effect. It’s too easy to have a fantasy game feel like a (more) fucked-up safari when each encounter is with a new creature entirely - and requiring less thought and care than having the unique situation be the interesting element in any given encounter. The world feels richer, each denizen worth investigating and understanding when they are not one in another chain of ‘one-offs’ - and those rarer, unique creatures stand out all the more for bucking the trend.
This deepening effect helps combat the presentation of the inhuman as ‘fair game’ - an empty Other, valid targets for all viciousness to be visited upon. The root of many monsters in V2M& being humans transformed by their own actions also helps with this - and this effect extends to those creatures which are not human in root, whether that be to underline that they have their own existence and motivations or to make their total inhumanity even more startling and uncomfortable.
In future, when developing a campaign setting, consider doing so ‘Monster First’ - and being very deliberate about using something from outside your initial list.