The side bar states that when drinking the potion, the PC's can make a Spot check (DC dependant on whether the liquid, or container is clear or not) to see if they notice they've swallowed something. How do I know what the potions look like to determine the DC?
There's an article in Dungeon 125 (the one with three faces) that has random tables for what potions look like. I use this when generating what a particular spell's potion looks like. (I should note I intend to generate a different appearance for a significantly different type of magic.) As to the vials, I'd either make it random, or assume they are clay (cheap and hard to see through).
Also, if infected the worms do some CON damage every day (If they fail their Fortitude save). How do I explain this to the PC affected? WOuld they have to make a check to notice they aren't as healthy (as their HP and Con decline, or would they know something was up the first time they fail their saves?
They know they feel bad. I'd say, "Make a Fort. save. You feel sick, take 1d4 Con damage. Maybe it is food poisoning." Treat it like a disease, but no number of successful saves will make it go away. I'm planning to allow a Heal check at the save DC to determine there is some type of parasite, and a check at the save DC + 5 to know it is an infestation similar to Kyuss worms. So no check to know there's something wrong, but a check to know what is wrong.
The potions with the worms were in darkened glass vials, according to the module. I made the mistake of not giving any special description of earlier potions the party had encountered, so the description tipped off my party that something was up. They had the wizard examine them thoroughly, and the wizard ran them through some alchemical checks. He rolled a 20 on his craft alchemy, so I told the party that when he strained the first potion, he found the worm.
The sidebar gave a DC for the spot check for opaque vials or dark liquids (DC 20 IIRC) to catch the worm as it goes down the hatch. If this happens, I'd give them a fortitude save to see if they can cough the thing up without swallowing it. If they fail that, then it's time for the CON damage. Come up with some appropriate symptoms that will clue them into the fact that they are ill, but not make the exact nature of the affliction too obvious. Then allow heal checks to determine the nature of the affliction--but set the DC high, since this is not a common affliction. Since the party has access to remove disease by this point if they have a cleric, paladin, or druid, a slow worm probably won't get the job done--slow worms work better on ordinary peasants who can't afford medical treatment. But it will give them a scare, especially if you describe the effect dramatically--like "a fat green worm crawls out of the victim's nose and falls lifeless to the floor. It quickly degenerates into brownish goo."
I would handle the Slow Worms the same as I handle disease.
If the PCs have the good sense to examine the potions prior to drinking them, I would allow for the Spot Check to notice the worms. Otherwise, I wouldn't say a damn thing until THE SESSION AFTER one of the fools actually drinks one down (then simply call for the PC to make a Fortitude Save out of the blue!!!)...
The reason for this is because;
1) - If you call for a Fort Save as soon as someone drinks a tainted potion, the party is going to get all paranoid and examine every potion they have until they have found all of the Slow Worms (which gives you fewer chances to be an evil DM).
2) - By calling for the Fort Save a session after a PC is infected, the Players aren't going to have any idea what it is that is causing their "sickness", and consequently may end up drinking another worm... Oh, they will eventually figure it out, yes, but let them squirm a bit (if you'll pardon the pun), while they attempt to locate the source of the Slow Worms.
I promise that as soon as someone looses some CON, the party will be casting Remove Disease, and their arsenal of curatives to try and locate the source of the sickness. Maybe even, let the afflicted PC hack up a slimey, dead worm, but still BE SILENT as to where they actually contracted the little bugger.
That's my two-cents!
I made sure that all mine were not transparent. Why would you know who want to hide the worms in a transparent potion.
After they drink a tainted potion I make them make the spot check, but I have the entire group do it and tie it to fake something else happening. That way they are not so quick to pick up that there might be something wrong with the potions.
edit: I like Drawmij's_Heir's idea better than mine! :)
I am running my party through the Encounter at Blackwall Keep and they are close to finishing up in the Lizard folk Lair.
My question is around the Slow Worms within the different potions. My party has snapped up the potions, so I need some help on how to handle it.
I actually kept a very, very bright side note behind my DM screen tracking exactly what potions fron the hoard were tainted. During a future roadside encounter with trolls, as soon as I heard a named potion being consumed and I was sure that they didn't already have a duplicate of said potion, I forced the roll on them. During combat, it is easy to obfuscate the roll for the potion versus another save versus a different effect. This is a dirty DM trick, but helps to suspend disbelief and thus is effective.
luckily enough i describe the colors of all potions encountered and so the pcs now know that a light blue-green potion is a healing potion. of course one time its gonna be poison or something and then throw 'em a curve ball :) as for the slow worm potions im having all the ones the lizardmen carry be in clay tubes so that they cant see inside and the mixture is too dense to see when the potion is just opened.
luckily enough i describe the colors of all potions encountered and so the pcs now know that a light blue-green potion is a healing potion. of course one time its gonna be poison or something and then throw 'em a curve ball :) as for the slow worm potions im having all the ones the lizardmen carry be in clay tubes so that they cant see inside and the mixture is too dense to see when the potion is just opened.
Match! Mine are the same colour, just with gold flecks in them. I think it's a left over from Baldurs Gate, NWN, or similar RPG.
The party love it when they find light blue-green potions, is such a perfect setup for this sort of thing.
Of course now i need to be accurate and track ALL the potions I give them... sigh, the joys of DMing ;)