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Using Poison and Disease Traps

by Jae
Poison and Disease Traps

Raw damage from traps is fine and all, but poison and disease traps can be so much more interesting! When filling a tomb, crypt, or other old creepy place, it’s never a bad idea to place some poison and disease traps. In today’s DnD Trap Tuesday, we’ll be looking at how to use poison and disease from the Core Rule Books to make a trap with a bit more punch.

Poison and Disease Traps Aren’t Always Conventional

A trap that uses poison or disease doesn’t always look like a trap. Often the assumption is that just because something is a trap in design that there must be an accompanying mechanical or magical component. This couldn’t be further from the truth with these hidden gems. Crypts are dirty places crawling with disease and everything in a swamp is likely poisonous. When you set up traps in these places, they are not the conventional switch or lever that players know to look for. Instead, sometimes the danger is just from the environment itself. Disturbing a tomb might lead to diseases long held dormant. Stepping too close to a scorpion’s home can get you stung. These are all traps in the way you place and design them, but they’re unconventional due to the fact that they are active parts of your world’s environment.

gross crypt

Conventional Traps Don’t Have to Deal Damage

Poison and disease can be just as lethal as dealing damage directly. You can have traps with all sorts of effects, but putting a mechanical or magical trap that appears to do little or no damage can be scary and unnerving to your players. For example, a trap that fires a dart at the player and strikes them but deals only 1 hp in damage seems like nothing. But later the poison kicks in and can affect them in so many ways! Disease is another effect that can come on without damage. A water trap floods a room with putrid water might cause no damage initially, but could inflict disease easily on the waterlogged adventures.

Types of Poison

Poisons come in many varieties and are described in detail on p. 257 of The Dungeon Master’s Guide. The DMG indicates that poisons have four main types: contact, ingestion, inhaled, or injury. You’ll likely use any of these but ingested for conventional traps, but there are a few traps that can make use of the ingested type of poison as well. After talking about types of poison the DMG goes on to list out the poisons available in the rules in a table and gives a name, type and price for each. More often than not your traps will have specific effects and may not be one of the poisons listed in the DMG. The descriptions that follow for each paint a picture of the effects that poisons can have. Rather than go over those descriptions, let’s look at the types of effects that poisons have and break them down into groups.

Poison Effects


Most poisons cause the poisoned status effect, which is described in the back of The Player’s Handbook. This poison gives players disadvantage on attack rolls and ability checks. While that might seem manageable, the duration of this is what makes it punishing. Beyond the poisoned status, many poisons impart temporary unconsciousness. This can be especially dangerous if the poison is the first part of a multi-part trap. While the poisons in the DMG don’t inflict any other statuses, you can always feel free to add any status you want to your own poisons and see how that affects your game!


Most of the poisons described in the DMG just deal damage directly. You don’t need to consider it the definite end all be all for poison. If you’re adding poison to a trap, the damage is often an unnecessary addition since you could cause damage in a variety of other ways. Classic poison damage stands apart from direct damage in that the save against them is using Constitution instead of Dexterity like other taps would.

Damage Over Time

Damage over time is far more interesting than just straight damage since you can have the players dealing with this progressively through a dungeon. Damage over time is usually every 24hrs and in some cases cannot be healed by any means other than saving against the poison or with higher level spells like Greater Restoration. These can make a long dungeon run seem very perilous.

Stat Damage

None of the given poisons in the DMG cause stat damage, but don’t discount it as a possibility. Stat damage can come in two forms: Raw numbers, which reduce a player’s stats until healed, or as Disadvantage on checks with that stat. These are both punishing in different ways and can be used to make other challenges in a dungeon more dangerous. By using these you may need to do more math than normal, but your players should be able to handle them if they aren’t too severe.

poison dart

Types of Disease

Diseases are like poison’s gross cousins. While the DMG has what it calls “sample diseases,” it does not have any hard rules for diseases and does not have a table of them. This is a great way to flex your creativity. Diseases can impart a lot of the same kind of disadvantages that poisons do. However, they come with their own set of rules and usually don’t have the poisoned status effect.


A disease can be picked up from many places: opening a tomb, encountering a sick monster, a cloud of dust from a trap. All of these are ways a disease can be picked up in the game. When a player first comes into contact with a disease, they may simply be infected or have a chance for a Constitution save to ward off the illness. The DC of these checks is up to you, but you should make sure if something has a high DC that the illness will have options for the players to deal with it.


Diseases are sometimes subtle and progressive when they appear. A disease might present symptoms within hours or not until days after infection. Players can carry a disease with them for a long time before they even know it. If you have a disease that has a long incubation period, a player may unknowingly spread the disease on their travels without realizing it.


When sick, a play may be contagious. Players within a certain range of an infected player or monster may need to check to see if they catch the disease. This can be done many different ways. One of the best mechanics to use is the uncertainty that comes with it. Your players may make rolls, but you never tell them if they pass or fail, they simply get sick or don’t after a certain time passes.


Disease symptoms can be as straightforward as poisons are, but they can also be extremely different. Giving players a level of exhaustion is common. There can be affects to their mind, causing fits of laughter or madness. There can be discomfort that prevents them from gaining the advantages of rest. Really you can tailor these for your game, but you should think about how you feel when you get a cold or the flu and then imagine adventuring while feeling like that.

Symptoms can also take the appearance of status effects. You can blind or paralyze a player with illness easily. Sometimes you can even set up progressively worsening symptoms that will indicate the player needs to rest or have a restoration spell cast on them before the symptoms develop too far. Make sure to use a lot of descriptive language so your players understand the severity of their illness if you are going to go this route.

Resistance and Curing

Players typically get to make Constitution saves against a disease every 24 hours or after each long rest. This doesn’t always have to be the case and you can decide if a disease requires magical or medicinal healing in order to be removed. If players pass their saving throws, they may have resisted the disease, but that does not mean they are instantly better; this may only mean that they are on the mend. One of the example diseases shows this by having each successful check reduce the DC for the next save and the illness is fully healed when the DC drops to 0.

When it comes to magically healing someone or using medicine to help them recover, it’s important to know how the players will be able to heal themselves before they try things. If Lesser Restoration will work, that’s great, but maybe a powerful illness would need more intensive treatment. For medicine, if you don’t have a particular plot relevant cure in mind, you can treat a successful skill check from the healer as a success on the disease’s saving throw.

exposed player

Sample Disease and Poison Traps

  • Animal bites (nests, small animals in tunnels or crevasses)
  • Cloud or Vapor traps
  • Tomb, Crypt, Swamp, or Sewer air
  • Disturbing corpses
  • Dart and Blade Traps (injury type delivery)
  • Food traps (great for intrigue quests)
  • False healing fountains
  • Flood traps and sewer waters
  • Exploding corpses or enemies
  • Sealed casks, chests, coffins, etc.

When to Use These Traps

These traps are actually a great set piece for most adventures into old and abandoned places. They make a lot of sense in any place that may be long forgotten or rarely traversed. Poison traps are more suited to places that might have more devious and insidious residents, such as a thieves’ hideout or assassin’s lair. In most cases, the use of these poison and disease traps can be a fun substitution for a straight up damage trap and present the players with non-standard challenges. These are best suited for mid-level adventures.

When Not to Use These Traps

These traps are too much for player groups without a main healer or low level parties. You can use them, but try to ensure that these traps won’t wipe a party entirely. Dying in glorious combat is one thing, but succumbing to disease is not typically a fun way to lose a character. If your party isn’t suited for these traps, scale down the effects or lower the DC ratings over time to ensure that they are not going to be too much of a burden without adding to the story or game play.

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For more walkthroughs and trap examples, check out our Complete Guide to DnD Traps article.

Happy DMing!

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