The majority of DMs run a campaign where low-CR creatures like kobolds, goblins, and wolves (which I’m going to use as examples) are restricted to low levels, never to be seen again as the PCs level up. If the creatures do make an appearance later on, it’s in ridiculous numbers or with a questionable amount of hit points. There’s nothing wrong with any of these approaches (I’ll give some advice on those later), but there’s a whole other option: guerrilla tactics. You may have heard of Tucker’s Kobolds but how do you go about making such tactics work in 5e, where combat is often weighted in the players’ favor at higher levels?
Guerrilla Warfare. Wikipedia defines guerrilla warfare as “a form of irregular warfare in which a small group of combatants such as paramilitary personnel, armed civilians, or irregulars use military tactics including ambushes, sabotage, raids, petty warfare, hit-and-run tactics, and mobility to fight a larger and less-mobile traditional military.” Simply put, if you can’t win in a fair fight, and you want to win, don’t fight fair. The term guerrilla itself is Spanish for “little war.” The mindset that you want to get into as a DM is that this is not a single battle, but rather a little war. The PCs are going to be slowly weakened by the attacks of the enemy so that if they do meet them in battle they’re going to have a much harder time defeating them. In addition, if the PCs are meeting these creatures for the first time they will usually underestimate them, making it even easier to challenge them. By the time they realize their error, they’ll have lost hit points and resources.
Playing the Long Game. Whether the PCs are venturing into a forest overrun with goblins or an underground nest of kobolds, their adversaries will harry them as they advance towards their goal, weakening them with attrition and denying them a safe place to rest. If the creature is a humanoid or at least semi-intelligent it will use other creatures to do their close-range fighting. Kobolds might unleash swarms of insects or even giant vermin while goblins might release a pack of wolves. They might try to poison a food or water source in the hopes that the PCs will avail themselves of it, or an individual may feign surrender or alliance in order to sabotage the PCs from within.
Running Beasts and Creatures With Low Intelligence. Creatures that have a low intelligence such as a wolf don’t have as many tricks at their disposal, but they can still be a significant threat if played the right way. What wolves lack in intelligence they make up in instinct. They may keep their distance until the PCs are weakened, resting, or separated. They will likely overwhelm a single target using pack tactics, and usually choose a target who is weak or weakened. With one target down they move to the next, retreating if they take significant losses.
Taking Inspiration From Early Editions. I really enjoy converting older content to 5e. One thing I miss about earlier editions of D&D is that the campaigns written for them often included enemy tactics for the first few rounds and whether or not the enemy would flee or fight to the death, and if it fled, how soon or what would trigger it. They often had situational bonuses where maybe an enemy has a higher bonus to attack if a certain NPC is present, like a less potent barbarian rage. Recently I converted a dungeon from a late-90s Dungeon magazine, which was largely a fun-house style dungeon. From the ground level up the house is plagued by jermlaine, or gremlins. These, for those who don’t know are 1 hp humanoids about the size of a large rat that, like kobolds, use traps and ambushes to deter intruders. There’s one particular room which, if entered, the jermlaine immediately lock the doors and unstopper an eversmoking bottle under the floorboards filling the room with smoke so that the PCs cannot see. After this, about three dozen of the creatures enter the room through their rat-holes and swarm over the PCs stabbing at them with tiny spears. Now, the spears do hardly any damage but a few of the creatures are using poisoned weapons, and there are 30+ of them total, all of which are heavily obscured. When my level 7-9 PCs reached this room only half the party went inside, and they were extremely low on hit points and cursing the day they ever met these things when finally someone broke down a door and let them out. In another encounter just five of the creatures descend onto a chandelier and pass around a lesser wand of magic missiles (For 5e I gave the wand more charges than a wand of magic missiles but it can’t regain charges). The first time they went through this room, the jermlaine surprised them and they passed the wand around each firing it once at a different party member.
Traps and Terrain. Kobolds are known for diabolical traps and ambushes as well as escape tunnels so small most PCs have to crawl through them prone at half speed. The few tunnels through their domain large enough for medium-sized humanoids are riddled with traps and defensible ambush points. Dragons often have kobold colonies in the smaller tunnels leading to their lair (their own access point is usually well hidden or extremely difficult to get to without flying, or both) because the little draconic folk not only revere the dragons and bring them treasure, but they ensure nobody gets in to disturb the dragon’s sleep (at least not with most of their hit points). Goblins have the ability to hide as a bonus action, meaning if they’re in partial cover such as standing in underbrush they can fire off an arrow, duck and move to another position where an attacker would have to beat their Stealth roll with passive Perception or use an action and make a successful Perception check to see them. Trick the PCs into fighting on the enemy’s terms, whether it be in difficult terrain, in a room full of cover for the enemy, a narrow tunnel, or restrained by a net or cage while the enemies hit them from afar. Underwater combat provides a whole different set of penalties and can be great for combat where the enemy isn’t hindered by being in the water. It won’t always be possible, but if a creature is naturally stealthy, setting an ambush and getting surprise on one or more PCs is a goal that should be prioritized.
Using Large Numbers of Enemies. I prefer to use smaller groups of enemies, but occasionally it makes sense to have a large number of enemies. Perhaps the PCs wandered into a lair and made so much noise the inhabitants came out in force or perhaps they stumbled into a patrol unit of an enemy army. Doing this where it makes sense can have great effect, but if a DM starts throwing more and more creatures at the PCs it’s going to get boring for them rather quickly.
Beefing Up Low-CR Creatures. I typically look at the stats in the Monster Manual as the average stats for a creature, and even though 5e doesn’t have rules in that book for adding classes or hit dice to a creature, I often do this. However, I reserve doing this mainly for “named” creatures. For those of you who aren’t video gamers, a named creature is one that is important enough to have a name or a title (even if your players never learn it), whether it be the leader of a kobold tribe or a huge goblin mutant with 150 hit points. You want to avoid just adding extra hit points to every single creature to drag out a fight. The longer a fight is the more variety and danger it needs and just adding hit points doesn’t give that. Assume a single hit will take out one of the creatures and work on making them harder to hit, and make it more likely they will hit their target. You can give a creature better weapons for more damage and better armor for higher AC, in addition to using previously mentioned tactics like ambush and terrain to grant them advantage and give their enemies disadvantage wherever possible.
Other Ways to Influence Difficulty. In addition to the more common methods above, there are still more ways to influence the overall difficulty of an encounter. One of them is by giving the PCs a quest or mission that hinges upon a certain task. Perhaps they have to escort an NPC with 10 hit points out of a cave of goblins or maybe they’re sent to negotiate peace with a tribe of kobolds and are warned not to use a single act of aggression on them. Another method is having an area be under a permanent magical effect or dweomer. Maybe a powerful artifact was destroyed in this particular dungeon and now magic works unpredictably here (you can use the wild magic table in the PHB or the wand of wonder table in the DMG for effects), or perhaps ancient wards prevent anyone from regaining hit points without using magic while in the area. Use your imagination, but make sure you have a reason for the dweomer to exist that makes sense, and drop clues about it in your dungeon. Below, I will tell you about a one-shot I ran that used both of these ideas.
The Luck Eater. I ran a one-shot a few months ago, because we didn’t have enough players to continue the main campaign, where the players were tasked with finding and returning a lost cat. Of course this was no ordinary cat but a luck eater, a creature from early editions that feeds on others’ misfortune (I have included my 5e stat block conversion below). It never attacks, isn’t particularly strong aside from its magical ability, but it is likely to leave a lasting impression on any who encounter it. Firstly anyone attempting a roll for pretty much anything within range of the luck eater has disadvantage. Making a roll feeds the creature. If it goes long enough without eating it can make PCs attack the first creature they see other than an ally (one of my players was forced to murder a random passer-by in Baldur’s Gate and cover it up). If it goes long enough without eating, it can make PCs even attack each other. In my one-shot, the two PCs found the cat after fighting a couple of cockatrices and one of the PCs was turned to stone. Luckily the other PC decided to leave their petrified ally behind while they returned the cat, because otherwise it might have gone badly while they were trying to lift the statue up the stairs.
In my next post, I plan on writing about how you can significantly increase the CR of a creature by adding class levels to it, and how to go about doing it.