By Nick Olivo
Your typical dungeon is populated with monsters, traps, and treasure. But there’s a fourth element, that, when incorporated properly, can make for a truly memorable game. And I’m talking about environmental hazards.
These are different from traps because there’s nothing to disarm, no Disable Device roll or Dexterity Check using Thieves’ Tools to simply bypass a problem. Players need to figure out how to best deal with these or how to avoid them all together, and that leads to some good role-playing opportunities, and can also make for some memorable battles.
Let’s take an example from a game I played in recently. My DM was running Storm King’s Thunder, and in one of the boss fights, we battled a stone giant priestess. That by itself was no big deal. The giant was a level-appropriate spellcaster who could summon earth elementals. If we were in a flat, open cavern, then the fight would’ve been pretty quick – surround and pound. But instead, the giant was on an island surrounded by a substance called gorgon mud. If you fell in and failed a CON save, your movement was reduced by half. If you failed a second time, you turned to stone. The giant and the elementals were immune to the mud’s effects, and so their main tactic was to try and push the PCs into the mud. We had two of the party turned to stone and the rest of us narrowly survived what was very nearly a TPK. It wasn’t the elementals or the giant that was the biggest threat here, it was the mud.
You can see how a very simple encounter can get ratcheted up to eleven by incorporating the right sort of environmental hazard. So let’s look at the different kinds of hazards you can incorporate.
Let’s start out with terrain. Lava is a nearly impassible barrier to low-level PCs, both blocking their path and dealing damage if they get too close to it. Normal mud can slow the party’s movement while enemies harry them with arrows and ranged spells. Rivers can split the battlefield and create chokepoints at bridges as the party tries to cross. Uneven ground or steppes will prevent the party from using ideal battle formations, and cliffs offer advantages to baddies that can fly. In caverns, stalagmites and stalactites offer cover to their denizens, to say nothing of the ropers that might be hiding among the stones.
You should also consider natural hazards, or hazards that may come about from the environment your adventure is set in. In many adventures, the PCs trek through sewers like they’re underground highways, and yet, sewers would be difficult terrain if the waste gets too deep, and slippery. There’s also a risk of disease from the filth and suffocation from gas build up. And there’s the possibility that said gas explodes if a sword causes a spark when it strikes an enemy, or if the wizard lets a firebolt loose at the wrong time.
A clever DM can employ other kinds of natural hazards. So if the PCs start a fight with monsters raiding a small town, maybe they set off a cattle stampede, and now the party has to avoid getting trampled while still fighting their foes.
And of course, we can’t forget magical hazards. These are things like the aforementioned gorgon mud; green slime, which drips onto players and deals acid damage; yellow mold, whose spores poison the players; and honestly, whatever else you can dream up. Were the ancient ruins the party just found the site of a massive human sacrifice? Maybe some of the terror and rage from that event still lingers in the structure, and if the PCs are standing in a particular location, they have to make WIS saves to resist going into a rage and attacking everything, or to avoid being frightened and losing their actions.
When planning your adventure, start out by figuring out what monster the PCs will face. Then, build out their lair. Ask yourself, what sort of environmental hazard would complement a particular creature? A fire-based creature, like a salamander or a fire mephit, is immune to fire damage, so lava won’t bother them. Heck, they probably bathe in the stuff. Let’s say the party is exploring an abandoned dwarven citadel, only to discover that the giant lake of lava that once powered the Eldritch Dwarven Forge is now a red dragon’s bathtub.
Undead are immune to poison, so yellow mold is just window dressing to them. Imagine a moldy old tomb, zombies and skeletons staggering around, setting off spores of yellow mold that poison the PCs. And now the PCs have to fight waves of undead while trying to make saves so as not to succumb to the poison’s effects.
The Dungeon Master's Guide and Tasha’s Cauldron of Everything both have sections on hazards and how to employ them. DMs should familiarize themselves with these and employ them whenever it makes sense. These small touches, sometimes as simple as adding mold to a room, can change the game experience completely. The party now not only has to figure out how to deal with the monsters, but how to handle the terrain, environment, and hazards those present. It can take what would normally be a simple undead-bashing adventure and turn it into a game session that your players recall for years to come.
