I thought this would be a good place to start, as it is one of the very broadest ways to classify your creature encounter. If we think about the real world and the abundance of variety provided to us by mother nature, we can see lots of good examples of different things that motivate animals into having some sort of encounter with humankind. We can also refer to some classic examples from movies, video games, and other media to provide examples.
We examine the possibilities below the jump.
Let's start out with the easy one. When we're talking about traditional gaming, what is the most basic reason for characters to come into conflict with a creature? Whether you're talking about demons from Doom, roving bands of Orcs in your fantasy campaign, or zombies in World War Z, these monsters are just evil. They're the bad guys, and your player characters are the good guys, at least relatively speaking. They actively want to do harm to others. This is a conflict that is hard-wired into the setting, and there's nothing wrong with that.
Malevolent monsters are an invaluable tool. They create rules for your characters to follow and create an order in the world. They provide clear obstacles with clear objectives. I love stories of moral ambiguity and blurring the lines between good and bad, right and wrong, as I think that makes for compelling gaming. However, if everything is colored in gray all the time, then it loses its edge. Providing a malevolent threat is a great way to keep action in your game, and to set up those more subjective bad guys down the road. It also gives the Game Master a great tool to help get your player characters into some trouble without relying on them to do it themselves (not that this is a common problem for most). Your malevolent creature can be actively on the hunt for tasty morsels such as your characters, thereby giving you instant cause to justify a combat event.
How do we design a creature with only bad intentions? We don't over-think it. These monsters give us an easy "tell" that they really are the bad guys. They might wear a certain uniform, reek of sulfur and brimstone, or just behave aggressively at every encounter. They seek out a fight with the player characters, attacking with little or no restraint. Whatever it is, it clearly identifies them as hostile, and provides a cue that a fight is about to break out.
This type of creature doesn't care about harming the player characters. It cares about something else entirely, but this affinity leads to potential conflict. This is the old "don't get between a bear and her cub" situation that we observe so often in nature. The trigger for conflict can be found in everything from a pack of wolves protecting its hunting ground from competitors to Gollum's obsession with his Precious.
Truth be told, most encounters with unintelligent creatures should probably fall into this category. Especially if your monsters are weird alien animals and not true agents of evil such as demons, vengeful spirits, or the like. Even if they don't know it, your characters probably bring most antagonistic beasts into a combative state by violating some boundary or tripping some trigger.
One of my new monsters for the Breachworld RPG, called a Hardhat, is overly-aggressive toward larger males of its species, causing it to charge and ram its opposition in an attempt to dominate it. This has translated to other creatures that it perceives as competition, such as large dinosaurs or trucks and wagons, while a person on foot has little to fear. The trigger for its aggression is simply that something it perceives as a rival has wandered into its territory.
The Hardhat, from the upcoming Breachworld RPG.
Art by David Arenas. Click for a better look.
To design a reactive creature, all you have to do is note the relevant cause and effect. Does the monster react violently to bright light or fire? Does it go into a rage if wounded? Does it savagely protect a fresh kill from other predators? It could really be anything. Remember that part of the fun of this sort of creature is that players can figure out the tricks to dealing with it, allowing their characters to grow by learning from past experience.
By alien, I don't mean that the creature is from another planet or dimension, but that it is something completely incompatible with the existence player characters. The creature and other people simply cannot coexist due to a fundamental difference in their very essence, which leads to inevitable conflict.
This relates a bit to the Hierarchy of Foreignness from the literary universe of Ender's Game. In one case (varelse in Card's parlance), a creature may actually be intelligent, with its own complex society and full sentience, but be so alien that communication and understanding are impossible. Such creatures might appear to us as monsters out of pure strangeness. Even if not intelligent in any sense, a creature's normal life processes could be enough to make a fight inevitable.
For an earthly example, consider a virus. A virulent virus conducts its business, living in our bodies and making us sick or even killing us, but it is not even aware that we exist. We can't communicate with a virus, or bargain with it. To preserve our own well-being, we may have no choice but to eradicate it. Just the same, the virus will continue to make us sick until it is eradicated.
For a gaming example, let's invent a semi-intelligent race of gelatinous blobs that must devour live blood to survive and reproduce. These creatures kill all squishy, fleshy life, human included, at every encounter. They do not recognize humans as anything but convenient sacks of blood for their dining pleasure. They aren't evil, or even inconsiderate. They're just so alien that if they are placed together with flesh-and-blood humans, it's kill or be killed for both parties.
Other examples might include the Formics/Buggers from the aforementioned Ender's Game (at least for the duration of the war), or traditional vampires that have no choice but to feed on humans as if they were cattle. Another great example comes from Season 4 of Star Trek: The Next Generation in the episode, The Loss, where the Enterprise is nearly destroyed through its accidental interaction with two-dimensional beings. This is definitely the rarest of the motivations found in our favorite games and other media, but it can be an epic adversary, or provide a great puzzle to solve.
There are all sorts of different nuances and combinations of the above, but I think most of your creature designs can fit into one of these categories. Considering this sort of thing in your design adds a lot of depth and detail, making your encounters rise above a pile of stats and dice, and those are the things that make your games really stand out to your players.
What are your favorite types of creature encounters? Any favorite monsters you've pitted against your players to great success?
Check out PART TWO and PART THREE as we start to discuss types of monster encounters.
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