Dungeons & Dragons Online

Simple and Easy to use System for Diseases!

Good day everyone! After lurking and stealing from here for a while, I feel like its time I give something back, or at least try to!

What is this and why?

  • This is a new system for diseases that is simple and easy to use, inspired from Darkest Dungeon.
  • It aims to be simpler than the disease rules in the DMG (256-257), as I personally find them to be unnecessarily complex and long (Cackle Fever is literally 5 paragraphs long).
  • Despite always wanting to use diseases in my games, I often forget to include them and even how they even work. Rereading them also takes too long!

Disease Rules:

Contracting a Disease

Whenever you come into contact with a disease, you must make a Constitution saving throw against the DC of the disease. On a success, you are not infected, but on a failure, the disease has infected your body and you begin to display the first symptoms when you take a long rest.

You make the check with disadvantage if you are bloodied.

Its important to have an idea of where disease come from so you can hand them out like hot cakes if you so choose. Most diseases come from infected peoples, contaminated items, eating rotted food or drink, or being attacked by vermin, insects, and animals.

In addition, a disease's DC does not represent how common or how deadly it is, but its survival rate, as you can have a deadly disease be a common occurrence, like the flu, or a not deadly disease be rare.


You can recover from a disease during at least 1 week of downtime, allowing you to repeat the disease’s Constitution saving throw at the end of the week, recovering from the disease on a success.

Alternatively, you may use magical effects or spells to recover from the disease, like lesser restoration, heal, or lay on hands.

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I find that downtime is something that most players often forget exists, or simple choose not to do as they'd rather keep following the adventure, so I make downtime sort of mandatory by requiring it for them to recover from diseases or to heal certain injuries.

Spreading Disease

While you are still infected with a disease, you are able to pass it onto other creatures by touch, through the air, or through death. Any creature within 5 feet of you or your corpse, or any creature that touches something you have contaminated, must make a Constitution saving throw against the DC of the disease you were infected by.

If players don't want to spend their spell slots on curing their diseases and don't want to do downtime, but still want to walk around villages and interact with merchants and rest in inns, their diseases may start to spread among the people they encounter. You don't have to roll for every person the player interacts with, probably just important NPCs, or you can also roll once for an entire community.

Example Diseases:

Cackle Fever (revised). DC 13. Gnomes are immune.
You succumb to occasional fits of maddening laughter. Any event that causes you great stress, including entering combat, taking damage, experiencing fear, or having a nightmare, forces you to make a DC 13 Constitution saving throw. On a failed save, you take 1d10 psychic damage and are incapacitated with mad laughter for 1 minute. You can repeat the saving throw at the end of each of your turns, ending the mad laughter and the incapacitated condition on a success. This disease only spreads when you are incapacitated with laughter.

Sewer Plague (revised). DC 11.
A general term for any illnesses which incubates in sewers, refuse heaps, and swamps, this disease fills your body with filth. You suffer from incredible fatigue and cramps, suffering from one level of exhaustion and regaining only half the normal number of hit points from spending Hit Dice and no hit points from finishing a long rest.

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Sight Rot (revised). DC 15. Requires magic or a special item to be cured.
Caused by drinking tainted water, this painful infection causes bleeding from the eyes and an eventual loss of sight. Your vision starts to become blurry with blood, causing you to have a -1 penalty to attack rolls and ability checks that rely on sight. At the end of each long rest after that, the penalty worsens by 1. When it reaches -5, you are blinded until your sight is restored by magic such as lesser restoration.

Sight rot can be cured using a rare flower called Eyebright, which grows in some swamps. If you have proficiency with an herbalism kit, you can turn the flower into an ointment which can be applied during a long rest, preventing the diseases from worsening. After 1 week of downtime, the ointment cures the disease.

Bad Humors. DC 8
Your humors have been thrown out of order! Your maximum hit points are reduced by an amount equal to 1d8. If your maximum hit points are reduced to 0, you do not die, you instead fall into a coma until you are cured.

Gear Rust. DC 15. Affects only warforged.
Your metallic joints painfully rust away, creaking with every move. While you are afflicted with this disease, your walking speed is reduced by 10 feet and you can't take the dash action. In addition, you have disadvantage on all Dexterity (Stealth) checks made to move silently.

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Yes, that's right! Not even those immune to diseases are safe!

Rabies. DC 12.
Your sight becomes blurry and your mind foggy, frothing at the mouth with an animalistic rage. You have a -2 penalty on all attack rolls you make, but have a +4 bonus to all damage rolls you make.

Scale Rot. DC 18. Affects only lizardfolks, dragonborns, kobolds, and other creatures with scales.
While infected with scale rot, your scales begin to soften and weaken, losing their color and slowly fall off your body. You have disadvantage on all Charisma (Persuasion) checks and all scaled creatures refuse to go near you for fear of them becoming infected. In addition, if you have the Natural Armor ability granted by your scales, you lose it while infected with this disease.

Tapeworm. DC 14.
A small worm has made its home in your stomach. You gain no benefits from consuming food or drink, and you must eat and drink twice as much to prevent starvation and dehydration. In addition, you only regain half the normal number of hit points from drinking Potions of Healing.


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