"Ah yes," He nods and replies for most the basic flower essences and roots for your home brew poisons.  (ooc: 1 gold per dose, max 10 doses).

Then you get to the talk about the dragon and other poisons.

"Well, I have good news and bad news," He tells you, "The good news is dragons are not generally immune to poison like many undead or infernals' are, so any poison could work.  The bad news, of course being, they are generally big and hearty and fairly resilient, especially to weaker poisons.  I do have a couple doses of purple worm venom, but that is not cheap- even for you."

"Wyvern venom is good too, but I am fresh out of that."  He pauses a moment, then smiles, "Its funny you say frost creatures... you know, if you happen anywhere near the Frostspine Peaks there are a lot of wyverns up there.  So much I would happily buy some off you should you be back in town and need to unload.  Just be mindful, there are some power things that live in those mountains."