D&D 5e - Questionable Arcana - Crafting: The Poisoner's Kit
Important Disclaimer: Although this crafting system leverages many existing 5e mechanics, the final product is completed home-brewed. Furthermore, some of the finer details are still being revised, and those changes will slowly be introduced into this document. However, the system as a whole is completely functional and ready to be used in any campaign. If nothing else I hope this document and its siblings can be used as a source of inspiration for whatever crafting system you decide to use.
I've finally seen my modifications to the 5e crafting system in action, and I must say I've been very happy with the results. However, in the course of explaining its mechanics to my players, I noticed some areas that still needed a little fine-tuning. In an attempt to flesh out the aforementioned crafting system, I'm going to do a series of articles featuring specifics from each kit. The first kit in the Questionable Arcana Crafting Series is going to be the Poisoner's Kit.
Before we begin, it's worth noting that the primary purpose of this article isn't to layer a bunch of new mechanics on top of what we already have. Don't get me wrong; there will certainly be additional mechanics and clarifications, but the idea is to go through a couple of crafting "case studies", helping other DMs apply the new crafting system manage some of the issues or loopholes you could encounter.
If nothing else, think of this series as something to reference when you need inspiration for uses of the system.
First, A Quick Overview of the Rules As Written (RaW)
The existing rules for extracting and using poisons harvested from creatures are pretty solid. You kill the creature and attempt a DC 20 Nature Check to harvest the poison, with a successful check yielding either a one-use poison you can apply to a blade for one minute or three pieces of ammunition. A failed check makes it impossible to harvest the poison, and a failure by 5 or more subjects the player to the poison. The effect of the poison is based on the creature's description, matching the effect applied after the target makes its savings throw.
If I were only allowing poisons harvested from creatures, this would be sufficient. It is simple, effective, and doesn't leave too much room for abuse (more on that later). However, the Rogue in my 5e campaign made it his personal goal to learn how to craft Floral Poisons. Being the generous DM that I am, I decided to do what I do best: run through dozens of hypothetical situations with Truck until we produced some concrete rules.
The Problem with Floral Poisons
5th edition doesn't detail many rules regarding plants, much less how to turn those plants into poisons. It doesn't even attempt to address the implications of a player who decides to try and create his own Brownroot farm in hopes of mass producing a furious bowel poison.
The gold-based crafting system works beautifully when all components are being purchased on the market. For example, explaining the crafting process of a garden-variety poison in the Adventuring Gear section of The Player's Handbook is easy enough. Essentially, you're trying to create a stable poison out of various household ingredients, which requires some pricey objects if you're buying in a normal market.
But what happens when a player creates the aforementioned Brownroot farm, enabling him or her to procure a massive glut of the poison's active ingredient? With the cost factor largely removed, things could quickly spiral out of control, ending with an entire party permanently toting poisoned short swords with overpowered effects!
The Solution to Floral Poisons
Rather than creating arbitrary limits on how much of a given herb you can harvest, I realized the cost mechanic could still be applied in this situation. As far as I know, there are no magical poisons in The Dungeon Masters Guide, so any plant-harvested poison can be considered a mundane item. Mundane items in both my home-brewed system and RaW have a base gold cost of 50% of the value of the item being created.
In this case, the best solution is to simply alter where the costs lie in the poison crafting process. The majority of plants the DM introduces as "craftable" reagents can't just be mashed up and applied to a weapon. Creating a stable poison requires a variety of chemicals and a great deal of steeping time to extract the poisonous effects from the plants. So even with a Brownroot stockpile, the majority of the costs remain tied up in other ingredients. With this modification, you're now able to apply a gold-based crafting process to plant-based poison formulas.
Your players may protest and point to real life examples of plants which can be immediately applied to a weapon. You can fold your arms and say they don't exist in your world, but there's no reason these simpler floral poisons can't coexist with the more complex. The party may occasionally find these "instant" poisons in the wild, but I recommend restricting the environments they grown in to avoid abuse. For example, a hypothetical Firevein plant capable of dealing 1d6 fire + 1d6 poison damage on injury can only be found on the slopes of an active volcano.
As stated above, the rules as written for extracting poisons from creatures are already fairly effective. A DC 20 Nature check, modified by your Poisoner's Kit proficiency, is very reasonable and also scales into later levels. Furthermore the rules already require that the creature either be dead or incapacitated, and the process itself takes 1d6 minutes. This greatly limits the players ability to harvest poisons from a live target, however there are a couple of loopholes the DM should be aware of.
The first and most obvious source of abuse is harvesting poison from a player-controlled pet or companion. Although most creatures eligible for those roles have fairly weak poisons, some notable exceptions could cause major power creep late into the campaign.
Let's say you allow a beast conclave ranger to choose a giant poisonous snake as a familiar. Because the snake generally follows your orders without question, a clever player might try to milk the snake regularly to amass a poison stockpile. Rather than disallowing this behavior, I'd recommend some simple restrictions.
First and foremost, I'd limit the milking rate to at most once per long rest. Secondly, I'd require more than one milking to get enough venom for a useful poison. If harvesting a full venom sac from a dead creature typically yields one dose, a milked creature would likely have a lower yield. Lastly, a "milked" creature loses the ability to apply its poison in combat until it has taken a long rest. This is typically only an issue for home-brewed classes, such as the 5e Beastmaster, but these rules will help avoid power creep.
The last potential pet-related loophole I want to cover is a player who decides to go all Matt Damon and make a zoo to house all the poisonous creatures they find. This could hypothetically grow into a never-ending source of free poison, but it can once again be easily managed by the crafting cost formula.
Any large-scale creature milking operation would require staff to maintain the buildings and feed/milk the creatures. You'd likely also need a consistent supply of antivenom to prevent loss of life in the event of a staff member getting bitten. You can itemize this, but I'd recommend assigning a value to the poison being harvested and utilize crafting formulae with the values shifted towards the maintenance of the facility. For example: 4 staff members proficient in the Poisoner's Kit harvesting poisonous snakes would milk 4d4*5+20 worth of venom per day from the snakes. If you assigned a value of 200 GP to the poison, it would take, on average, just under 3 days for the team to produce a unit of venom.
In the event that a character attempts to sell any poison on the market, I would limit the volume they are able to sell. I recommend using the RaW rules for selling a magic items on page 130 of The Dungeon Master's Guide.
Poisons Derived from Magically Created Material
There are a couple of spells in the game that could potentially be used to create poisonous materials. The biggest offender would definitely be the Creation spell which allows for the creation of non-living vegetable matter for up to a day. The relatively short duration should disallow crafted poisons such as the hypothetical brownroot poison discussed above.
However, a shrewd player might try to create a large amount of instantly usable poison such as the firevein example from above. In this case I would actually recommend that you allow this behavior, but with one important caveat, you need to strictly enforce the material requirement of the Creation spell. Creation requires a tiny piece of matter of the same type of the item you plan to create. This means that the caster needs to have some of the poisonous material in their possession to be able to create it. Granting the entire party poisonous weapons is actually an appropriately powerful effect for a 5th level spell, and requiring the party to have previously encountered the poison allows the DM to manage the power level of the poisons the party can create.
The last loophole I want to cover is if a magically summoned poisonous creature such as a familiar, conjured animal, or wild-shaped druid attempts to create a poison. This situation is easily managed by using the same poison milking rules listed above for pets. This essentially creates a trade-off of requiring the use of a spells/wild-shape and additional spells to incapacitate the creature for some temporarily usable poisons. The poisons are temporary because any poisons harvested from the magically created creatures only stay in the world as long as the magic is in effect. Once the magical effect ends all unused poisons disappear. However, it is worth noting that any damage dealt from the poison stays in effect, however any statuses linked to a long-term poisoning such as the poisoned effect should quickly wear off once the poison disappears.
Eventually a party member will get the brilliant idea of mixing all of the poisons they have in a jug and using it as a bottomless well of murder ink for their sword. To handle this situation, just dilute and combine the effects proportionally. If you take a poison that causes paralysis for 6 rounds and mix with with a poison that deals 2d6 damage hit, the product would be two units of poison that paralyze for 3 rounds, dealing 1d6 damage on hit.
Optional Rule: The process of mixing poisons causes the individual poisons to lose some of their potency. With this rule in effect, the example mixture above would only paralyze for 2 rounds and deal 1d4 damage on hit.
These rules and standards hopefully clear up a lot of the gray areas around poison crafting. We now have some concrete rules around creating plant-based poisons, and have addressed some of the major loopholes surrounding creature-based poisons. Much like the base crafting system, I did my best to avoid creating new reagent and rules tables. However, if your party has spent a bit too much time playing Stardew Valley and decides to open up the world's sketchiest family farm, this system can be expanded to accommodate their needs.