Blog

RPG Ideas — Parasites

Welcome once again to the weekly newsletter. This week’s topic is parasites, which we discussed in our weekly live chat. We hangout every Monday evening at 8 p.m. EST on Nerdarchy Live to talk about D&D, RPGs, gaming, life and whatever nerdy stuff comes up. Speaking of parasites our fully funded Mage Forge project nears completion but it can still benefit from the nutrients provided by your support. And you’ll get a huge collection of magic items in return! In our recent update we shared the Spirit of the Mage Forge encounter to pull together community inspired ideas and build on them while adding some fresh takes and more dynamic elements for better player engagement and story potential. Learn more about Spirit of the Forge and how to get your FREE copy here! You can get the Nerdarchy Newsletter delivered to your inbox each week, along with updates and info on how to game with Nerdarchy plus snag a FREE GIFT by signing up here. You can get the Nerdarchy Newsletter delivered to your inbox each week, along with updates and info on how to game with Nerdarchy plus snag a FREE GIFT by signing up here.

Nerdy News

Make sense of the week that was! Discover new magic items on campus, balance the scales of justice as a Devil of the City and scratch your head over some nonsense plus new live chats with industry pros and creative folks and live game play rounds out this week’s Nerdy News. Check it out here.

Delving Dave’s Dungeon

Nerdarchist Ted came up with this topic. Parasites make me think of some of the worst aspects in earlier editions of Dungeons & Dragons like rot grubs. These beasts were introduced to 5E D&D in Volo’s Guide to Monsters as the swarm of rot grubs, which are brutal but not compared to AD&D rot grubs. I know they aren’t exactly the same but the idea of save or suck is still there. Typical parasites aren’t easy to combat or even detect.

There are a couple of ways to handle parasites in an RPG. You could treat them like diseases. Parasites could be a problem to solve or overcome. People get sick or die in a discrete area and investigation from the group reveals the food or water is contaminated. Is this by happenstance or design? Now you’ve got a mystery adventure for the characters to unravel.

Another way you could expand parasites in an RPG is a bit more fantastical. Consider parasites that feed off of souls, psychic energy, dreams, technology or even magic. These could be more like traditional monsters you are used to finding in RPGs.

One classic monster really stands out as being a parasite — vampires. They need the life energy of other living things to sustain themselves.

A few examples of parasites are tapeworms, fleas and barnacles. A science fiction or fantasy spin could present these parasites as intelligent creatures who ride along in other creatures. In this case it might be a while before the characters understand where the true threat lies. They defeat a threat only to have the parasite move to a new host. This common trope in science fiction and supernatural stories is great for mystery and horror style adventures.

But there’s no reason you couldn’t do it in a fantasy RPG too. A demonic parasite works for this concept. Entities from other dimensions and undead monsters could be another source of inspiration and power for the parasites. What about a parasite that conveys power on its host no matter its origins? Everyday folks become super strong or exhibit supernatural powers while these parasites live inside them. This presents a quandary for the characters to deal with and overcome without unduly harming the otherwise innocent hosts.

From Ted’s Head

This was a great discussion when Nerditor Doug and I chatted about it. Parasites are a strange area. They are technically alive so they’re not a poison or a disease. They can be either partially harmful while being partially beneficial or can be wholly harmful.

In the chat I pulled out 3.5 D&D’s Expanded Psionics Handbook and read about

cerebral parasites, which are parasites meant to reduce psionic power points. Diseases are a bit of a joke in 5E D&D edition unless you alter spells and nerf a paladin’s Lay on Hands feature. But if you introduce a parasite requiring something more than either of those abilities it could be really nasty.

Since 5E D&D steers away from psionics conceptually or treats it no different from other spellcasters I could recreate cerebral parasites but make them drain spell slots (or equivalent spell points if you are using the alternate rules in the Dungeon Master’s Guide) instead. Allow me to introduce you to Magus Parasites.

Magus Parasites

Magus Parasites are minute vibrant blue flecks to the naked eye. Once they get on you they remain dormant until you use a spell slot to cast a spell. When this happens they painlessly burrow beneath your skin and begin tapping into your magical reserve. At the time they begin to burrow you can make a Constitution saving throw to shrug them off. If you fail the saving throw they are inside and very difficult to deal with.

In order to make magus parasites useful throughout all tiers of 5E D&D play see the list below for DCs and effects. Normally your spell slots would be restored when you complete a long rest. But a magus parasite infection instead consumes a portion of your spell slots. As these parasites live in you they continue to grow and multiply. Sadly, you can spread them to other creatures provided they have spell slots to consume.

Magus Parasite Infection

Saving throws and spell slot damage are based on the infected character’s proficiency bonus. Calculating spell slot damage is easy. Once you roll to see how much they have consumed that day this spell slot damage represents the total levels of spells consumed. The affected spellcaster can determine how they want to spread it out.

For instance a 5th level druid is infected by these nasty buggers. They fail their saving throw and take a long rest. I roll 2d4 and get a total of 3 for the spell slot damage. The druid can either lose one 3rd level, one 1st and one 2nd level or three 1st level spell slots. These are expended as if used. If the condition is cured the slots come back naturally when a long rest is completed. Rolls are not cumulative and begin fresh each day. A spellcaster under this condition is aware they have less magic than normal but might not necessarily be aware of the cause.

• Proficiency Bonus +2. Constitution Saving Throw DC 13, Spell Slot damage 1d3
• Proficiency Bonus +3. Constitution Saving Throw DC 14, Spell Slot damage 2d4
• Proficiency Bonus +4. Constitution Saving Throw DC 15, Spell Slot damage 3d8
• Proficiency Bonus +5. Constitution Saving Throw DC 16, Spell Slot damage 3d10
• Proficiency Bonus +6. Constitution Saving Throw DC 17, Spell Slot damage 6d8

If you think this is too dangerous and want to treat it like a regular disease feel free but if you want it dangerous for a bunch of spellcasters it could require a skill challenge using Medicine, alchemist’s supplies, Arcana or similar challenges your group feels makes sense. Diagnosing a magus parasite infection could require a magical ritual to suffuses your body with so much magic the creatures gorge themselves to death. What about the opposite? Do you have to spend three days in an antimagic field starving them to death? However you play it use the DCs in the list above for saving throw and skill challenges.

As a side note I will add that cantrips are completely unaffected by these parasites. I would not want to completely drain a spellcaster of all of their abilities and make them useless, which would be cruel. But introducing a challenge like this should be something to truly present an obstacle and characters who come out on the other side should be rewarded. Once defeated do the magus parasites leave a little extra magic behind? Be careful and have fun with this bizarre creation.

From the Nerditor’s Desk

I can’t help thinking of the comic book supervillain Parasite, one of Superman’s recurring adversaries, ever since Nerdarchist Ted pitched this topic for discussion. This classic character’s been around since 1966 in various iterations but what’s cool about Parasite is rather than the villain being infected by parasites instead exposure to strange energies from outer space transformed a normal person into a parasitic creature.

Thinking of parasites as an infliction that fundamentally changes the host creature introduces something of a sympathetic quality in dealing with the situation too. This puts in mind another creature from fiction — the “salt vampire” antagonist from the Star Trek episode The Man Trap. This creature from planet M-113 represents a grave threat to the crew of the USS Enterprise.

Can parasites become evocative plot devices in your RPG experiences?

Whether you’re playing fantasy, science fiction or even non-genre games the idea here is parasites as living creatures with some sort of agenda coupled with either creating a fundamental change in the host like DC Comics’ Parasite or a method of remaining undetected as anything other than a member of the existing population like Star Trek’s salt vampire. Both scenarios include plenty of opportunity for conflict but what I also dig is the idea these parasitic entities can evoke compassion or at least understanding from the players.

The juice for your RPG lies in whatever the parasites require for survival, which in both cases comes from an external source. Rudy Jones is transformed and the salt vampire simply follows a biological imperative but they both become dangerous to those around them simply through their attempts to survive. There’s a ton of great storytelling you can hang on these themes. Can the heroes separate the parasite from the host, who becomes something of a victim themselves driven by the compulsion of the parasites afflicting them?

Introducing these kinds of parasites to your RPGs through NPCs is your safest bet because a GM has total control over them. The trick is conveying to the players something different or off about their behavior. Star Trek’s salt vampire ups the ante considerably because the creature can also shapeshift into forms known to those around them by telepathically reading memories to create a false sense of security in their prey. The supervillain Parasite can also absorb knowledge from his victims too, and some versions could control their own DNA to such a degree they could literally become the people they drained.

Adventures involving parasites bring lots of intriguing concepts to the gaming table. Identifying the parasitic nature of the threat presents the first challenge, which might be incredibly difficult. Next the characters can work on figuring out the origin of these parasites and devising a way to determine who’s afflicted. Then the challenge moves into much deeper territory. Can the parasites be separated from the host without causing even further harm? If not what other options do the characters have available and how far are they willing to go?

*Featured image — A lone parasitic cerebug lies in wait on a peaceful farm awaiting a bloody appearance and targeting one character as its new host in Passenger, one of the 55 dynamic encounters ready to drop right into your games from Out of the Box. Learn more about all of them here.

Subscribe to Nerdarchy Live and get notifications for live RPG game plays, chats with creators and industry professionals and new video series and content on our second YouTube channel here