I have a player in my current campaign that wants to make use of poison, the limited rules on poison i've found thus far are just that, limited. Are there more sources than i've discovered for 5e or am i better off hitting up an earlier dnd version and adapting those poison rules to 5e.

I want for her to have some cool poisons to make use of, but i don't want it to be overpowered. I suspect i'm going to have to do some DM handwaving of the rules here to get this working. 

I know that there is a poisoner's kit and i found the rather generic poison vial which does 1d4 dmg on a failed DC10 con save (which, lets face it is not that hard to pass). I know there is a pretty cool magical poison dagger out there, but i suspect she's after something more mechanical rather than magical as it suits her character style. I guess i can reskin that weapon to make it more mechanical, i.e she has to forage for appropriate gear and make it into poison vials that she can reload into the hilt or some such. This would give the option of different poison types too.

Consider allowing her sneak attack to deal poison damage.  It'll be a slight advantage, but nothing you can't mitigate and will add fun flavor.

Edit: Yes, the poison rules are pretty limited.

Edit 2: Or not, https://www.dndbeyond.com/sources/basic-rules/running-the-game#Poisons Not sure how I overlooked/forgot about this.

 None of these suit your purpose?

https://www.dndbeyond.com/equipment?filter-search=Poison

The Serpent Venom poison looks like a good candidate for blade dosing. The save is low but, you still take half damage.

The biggest issue with poison is the cost. Poison is ridiculously overpriced. I highly recommend as Acme suggested to turn the sneak attack damage into poison. It is more a nerd than a buff, but will give you the poison flavor your want. 

I'm going to come up with a DC chart for foraging for poisons using survival or nature, and then another DC chart for turning those foraged parts into applicable poisons.

Cause yeah, those costs vs those DCs are a joke. 2000g for a DC 17. 

It goes back the original dnd where apparently they wrote poisons as being mostly useless when compared to magic as they wanted magic to be the fancy magical thing, and poisons already exist in our world and they wanted a separation.

So i reckon i'll use the charts of existing poisons and let the players find and make them, and i'll add in some costs to keep up the poison brewery etc. Plus any mechanical devices required for usage.

Best way to circumvent the costs issue? Multiclass as a Conjuration wizard, and maybe taking the thief archtype from rogue if you really want to do poison things. Basically all the official poisons we have aren't considered magical, so you would be able to conjure any poison you had previously seen. purple worm poison is 2k gp and has the 19 con save for 12d6. thats more than a fireball. So with this build, before combat you just conjure poison, considering you do it for free and it lasts an hour, I'd be willing to say that you just develop the habit of making it every 40 minutes or so. Bonus action from thief rogue fast hands lets you poison your weapons/ammo, then main action for attack. Just assuming something simple like a light crossbow and your at the minimum level for this which is level 5 for both archtypes, your doing 1d8(crossbow) + Dex bonus + 2d6 (Sneak attack) + DC19 Con save for 12d6 or half

Obviously the biggest flaw is that poison has the highest number of resistant or immune creature. The con save also, while not the worst thing in the world, is a stat most monsters have a decent score on average. Your still looking at most things being a lot more likely to fail than not though.

This build also just means you barely need to carry any niche gear, you can always have rope on hand, you can always having a climbing kit, thieves tools, 10ft pole, etc. on top of any other of the niche poisons. Your character, while a rogue, actually has an amazing claim for party loot just because other than maybe a full wizard you have the best use for it by buying/unlocking the poisons as well as obviously just being a low level wizard.

Also adding to this, the damage poisons aren't the only ones you can use in combat, you can probably manage to use any of the types other than ingested, many with horrible effects. Things that will knock enemies unconscious, paralyze them, and other debuffs. You have enough variety that as long as you fight things poison actually works on, you end up being a fairly versatile debuffer and damage dealer with the decent level of utility of a low level wizard.

The Minor Conjuration ability doesn't have enough reasonable limitations. I wouldn't allow a character to conjure a high cost, deadly poison as their "object".

As cool as your suggestion is Mobile, it won’t fly at 95% of DM tables and for good reason. Most will say you can conjure a vial but not a vial with poison. And that you must conjure an object not a liquid / organic material.

The thing about poison is that it is only limited by its cost. For the next minute after it is applied to a weapon, every attack that lands has to make a save and/or take extra damage and effects. It stacks with magic items, class features, and weapon enhancing spells.

And that is just for injury poison. Most of the other poisons will end combat before it even begins. I would absolutely allow them to be made/harvested by any character proficient with poisoner's kit, and I might adjust prices by up to 50% depending type.

Minor conjuration might be taking it too far. For one thing, it is hard to determine what counts as taking damage. Best case scenario it deals damage and has little to no lasting effect. (Minor conjugation absolutely can conjure organic material. It's an object as long as it isn't alive.)

Ok, so if cost is a major stopping point why not give them the opportunity to harvest various venoms from creatures.  A successful check gets you a few doses, a 'near miss' gets you doses with a lower DC.  A fail afflicts you with the poison and no doses are gained.  Would give reason to hunt down some venomous vermin.  Just take the stats for their poison attacks for the doses.  The scarier the prey the better the poison the harder it is to harvest.

Harvesting from creatures will be a total thing with me running the game, i'll definitely allow and even encourage that.

As for pure damage poisons, i'll probably not allow something like the purple worm poison to be easily found as it is worth that value and does a lot of damage, so it needs to be difficult. In fact, i'd probably say it could only be harvested from certain things and only with a successful check.

From what the player told me, she wants to do more than just some extra poison damage, she wants to do some roleplay stuff with it, like maybe slipping it into someone's food/or drink to interrogate them or something like that. So, sometimes i'll allow the rule of cool to auto fail the DC if she can do that, but in combat there will always be saves.

And you're right, there are some poisons out there that if the target fails their save, is almost an instant win in a fight. So it's not like i'll just let that stuff happen all the time. 

Quote from Stinkingyeti >>

Harvesting from creatures will be a total thing with me running the game, i'll definitely allow and even encourage that.

As for pure damage poisons, i'll probably not allow something like the purple worm poison to be easily found as it is worth that value and does a lot of damage, so it needs to be difficult. In fact, i'd probably say it could only be harvested from certain things and only with a successful check.

 Needing to kill CR 15 monsters (purple worm) to get the poison is probably enough of a cost, especially if they decide to burrow and hide if they start getting seriously hurt.

As a rogue you could try stealing from the rich, sell through a fence, and use the gold to pay for venom. If you have the Criminal background you can use your Criminal Contact as a fence/supplier of venom.

At higher level the costs become less of an issue, especially if you have a Wizard friend. One dragon trasure hoard and you could outfit yourself with lots of poisons.

Also, do remember when using poisoner's kit, you can basically craft it using crafting rules at half cost. That's the point of the kit: halving the cost.