There’s a D&D joke that’s gone around the internet a few dozen times about Mimics. “The barkeeper asked why we carried weapons on us in the bar. I said ‘Mimics.’ The barkeeper laughed, the party laughed, the table laughed, we killed the table. It was a good time.” It does a good job of illustrating the potential dangers a D&D party might face and why most tabletop players have a heavy dose of what we like to call “adventurer’s paranoia.” It’s the idea that almost anything can wind up wanting to attack adventurers and crazy things like chests that want to eat you, talking tables, and ceilings that decide they want to invade your personal space are all relatively normal.
If you spend any amount of time looking through D&D source-books, you find a whole slew of things specifically designed to be hidden until they’re eating you. There are all manner of horrible tree or stump creatures that will destroy an unwary party, not to mention all the horrific vines, lichen, and fungi that will kill you before you’re aware they’re trying. Then there are the ravenous beasts of the various wildernesses, territorial intelligent monsters, magical traps, and let’s not forget the Demons/Celestials/Fey who sometimes just want to screw around with mortals because they’re bored. Chairs come to life, the suits of armor in castles are almost always going to attack you, paintings can hide mesmerizing or mind-control magic traps, and even something as simple as a hallway can turn into a deadly gauntlet of hidden pits, spring-assisted blades, and magical fire at a moment’s notice. Carelessness causes death and only a screwy mind filled to the brim with paranoia can save you and your allies.
That being said, a lot of D&D campaigns don’t make use of all of these things. Traps are difficult to set up and often unrewarding from a DM’s perspective because two skill checks can bypass them entirely. Bringing the outer-realms of existence into the mortal plane is often a decision made by the story the DM has set up or the players have started, and that’s a hugely complex set of worlds to bring into any game without sufficient preparation. Everything takes a lot of work to set up and the players often wind up avoiding all of your preparation in favor of some unexpected route that doesn’t fit anything you’ve made. Monsters and encounters created off the cuff are rarely as creative and unique as the stuff you’d spent a week of evenings planning.
In my experience, you best bet is to always make sure to include a few intelligent monsters. If they’re smart, it means they have likely survived for a long time and have a wealth of experience to draw on when it comes to screwing with the party. Sure, the hallway doesn’t have any traps, but maybe a fleeing monster ruffled the carpet a bit because he knows the adventurers following him will be proceeding carefully. If they think there’s a trap, they’ll take the time to be thorough, giving the monster and its allies time to better prepare.
Ambush predators are almost always intelligent as well, with a whole history of successfully managing to prey on inattentive mortals. There wouldn’t be mimics pretending to be treasure chests if it hadn’t worked really well for a long time. Maybe one of them is smarter than the others and uses the shapes of its less-intelligent brethren to guide its own decisions. My favorite example of this was a mimic my party encountered. Elsewhere, there was a mimic as a treasure chest and a mimic as a door, so this one decided to assume the shape of the door frame rather than the door, because it knew it wouldn’t catch anyone off guard if it was just another door.
It is important to remember that, just because the creature is a monster doesn’t mean it’s fine dying or an idiot. Yeah, it would probably suck for your party’s caster if the monstrous stump attack it first, since the caster has so few hit-points and no ability to resist the monster’s poison, but why the heck would a tree stump smart enough to hide and attack opportune prey attack the armor-covered party tank who could shrug off all its hits? Controlled monsters require specific direction to differentiate, but any free-willed creature should be able to tell the difference between an easy target and a difficult one.
If you’re looking for ideas to justify your players’ paranoia, the internet has some really great ideas. Homebrew monsters are fine since all you need to do is make sure it isn’t going to be an unfair, unwinnable fight. If you’re looking for this sort of thing, you’ve probably gotten fudging things well in-hand, so being able to take the idea of an overly powerful homebrew creature and bringing it down to being an appropriate challenge for your player should be easy. If the world is really as full of dangers as they players think it is, make sure not to let them down, you know?
When it comes to other creatures, like goblins and kobolds and anything intelligent, the idea that they’re willing to fight to their death is a little far-fetched. Maybe the fight was brutish and short, like the time my party killed three rocs in the time it took for them to make a first approach, but any drawn-out fight should mean the losing party has the chance to surrender or flee. No squad of goblin soldiers is going to fight to the death without some level of magical compulsion or incredible fear of whatever is directing them. Or they’re fanatics. Fanatics love fighting to the death. Just make sure they’ve got weird tattoos, clothing, and jewelry.
Just make your monsters interesting if your players want a little depth or fanatical and crazy if they just want to kick down doors and kill stuff. Monsters should reflect the your setting’s level of realism if you want your sessions to be believable. Good monsters and enemies are an important part of making the game feel real for your players.
Honestly, I could probably do an entire week of posts on making good monsters. This catch-all post feels a little scattered to me, so I think I’ll revisit this once I’ve finished developing (and running) the dungeon my players are about to face since it is going to be all about realistic, intelligent, and creative monsters. This is going to be a lot of fun for me and will hopefully give my players the opportunity to rise to new challenges.