Infested: Parasites For Your Game

There are thousands of ways to die, millions if you’re really creative. I would take any of them over what did that.”

– Kinsey Stafford, Apprentice Field Medic

Adventurers seem to have a habit of going to great lengths to put themselves where they don’t belong. Traversing far-off mountains, exploring dense jungles, or crossing shifting deserts means risking many dangers—both seen and unseen. And before any inexperienced party heads off into the great unknown, they’re often provided with words of warning and wisdom from their more experienced peers. 

  Told in no uncertain terms that there are ravenous beasts, evil hordes, and supernatural monsters waiting to pounce in the wild places where adventurers are driven to explore, a fresh-faced group might feel emboldened by the knowledge that’s passed their way. But although knowing how to spot and avoid a massive danger will surely prolong the life of a traveling hero, sometimes the gravest threats that these areas contain come in the smallest packages. 

Content Warning

This new game option introduces an element that some players may find too disturbing to enjoy. Beyond the painful and often grotesque physical symptoms that accompany parasites, these tiny scourges can also bring about feelings of invasion and violation that characters must overcome. 

  Whereas some players may find this to be an enjoyable (if somewhat disgusting) obstacle for their character to face, others might find that exploring these particular themes in any way ruins the fun of their game and potential story arc for their character. 

As with all new rules and game options, it is highly recommended that potentially including parasites in your game is discussed during your pre-campaign conversations or during your group’s session zero. 

Parasite Mechanics

Beyond adding a layer of revulsion and paranoia, parasites bring a new condition into the game along with them—infested. Unless otherwise stated in a parasite’s description block, any spell or effect that detects disease or poison or ends disease or the poisoned condition will detect parasites or end the infested condition as well.

The effects of being infested are as follows:


  • An infested creature has disadvantage on Constitution saving throws and Wisdom (Perception) checks.


In addition to the infested condition, most parasites cause unique effects that are detailed in their description block. The Effect section of a parasite’s block describes the duration, damage, and any other ramifications that an infestation from that parasite may cause. 

Becoming Infested

Each parasite’s description block indicates how a creature becomes infested with that particular parasite by specifying whether it is external or internal. External parasites are typically contracted by passing through and coming into physical contact with an affected area or object. Internal parasites are generally contracted by a creature introducing the parasite into its system by drinking or eating contaminated materials or receiving an injury from some infested creatures. 

Detecting Parasites

Parasites, much like diseases and poisons, cannot be detected by nonmagical means, although a discerning character could make an appropriate skill check (Arcana, Nature, Medicine, or Survival) to realize the symptoms in another creature and tie them to the parasite in question. The DC for such checks should be determined by the GM as is appropriate to the circumstance.


Particularly adventurous characters may attempt to harvest parasites for later use. Should a character detect or discover a source of parasites, via magical or nonmagical means, they can follow the standard rules for harvesting poison to do so. Should they succeed in their necessary skill checks as determined by the GM, they can harvest one use of the parasite. If they fail, they are infested and subjected to the parasite’s effects as normal. 


Outside of spells or features that remove the infested condition from a creature, the most common way to remove parasites is through the use of an antiparasitic. Any character who has proficiency with an Herbalism Kit may create a single dose of a basic antiparasitic over the course of two hours if they have the necessary materials available. 

  It should be noted that anything that ends the infested condition on a creature will also end the effects of the parasite affecting them. 


Adventuring Gear

30 gp

This potent tincture provides a creature with advantage on saving throws against infestation for 1 hour or ends the infested condition in a currently affected creature.

Some parasites are more exotic, virulent, or magical than others, and require one or more special materials in order to make an effective antiparasitic to prevent or treat their infestation. If special materials are necessary, they will be listed in the parasite’s description block. 

New Parasites

The following are new parasites that you can introduce into your games. GMs should feel free to use the below as templates for creating their own parasites for later use or to alter the saving throw DCs, durations, or descriptions of those provided to better fit their campaigns. 

Dream Eaters (Internal)

Dream eaters are leech-like creatures that inhabit the sands of deserts beaches. They spend most of their lives in hibernation among the dunes, only waking when they sense the presence of a warm-blooded creature in their vicinity. Those unfortunate enough to make camp among the dream eaters stir these parasites from their slumber, causing the worms to slowly climb from the sands and make their way up and into their victim’s ear canal. By the next morning, the throbbing pain in the affected creature’s ears combined with the constant scritching of the dream eater’s movements makes sleep and concentration nearly impossible. 

Effect: Dream eaters cause incessant pain and irritation in the ears of those they afflict. A creature subjected to this parasite must make a DC 13 Constitution saving throw. On a failed save, it is infested for 2d4 days, has disadvantage on Constitution saving throws to maintain concentration, and cannot complete a long rest. On a successful save, the creature is infested for 2d12 hours.

Storm Mites (External)

Storm mites are aquatic arthropods roughly the size and shape of a copper piece. In most circumstances, these creatures remain in the shallow tidal pools where they’re born without ever coming into contact with people. However, during periods of monsoons and flooding, minuscule storm mite larvae are swept inland where they burrow under the skin of anyone that they touch, creating excruciating clusters of boils and making it almost impossible to wear anything heavier than a loose tunic. After they’ve finished incubating within their host, the immature mites burst out of their host’s flesh, causing even more pain and trauma to their victim’s body.

Effect: Storm mites burrow into the skin, causing painful and grotesque boils where they gather. A creature that comes into contact with this parasite must make a DC 15 Constitution saving throw. On a failed save, the creature is infested for 1d6 days while the mites incubate. During this period, the pustules caused by the incubating mites make wearing light, medium, or heavy armor impossible. At the end of their incubation period, the mites burst from their host’s skin, causing 3d4 damage.


Want additional parasites, infesting spells, and creature features? You can purchase this full supplement on DriveThruRpg or Ko-fi, or you can subscribe to our Ko-fi or Patreon and receive this title as part of a full sign-on bundle!

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