See if you create the device as just poison.
Then make a note that it is an "Open" link. you can choose what to link it to. Then add a quirk "Must some how enter the body" combined with "requires move activation" to link it to something.
Then you can freely link it to a dagger... a sword... an arrow... a drink.
Ya. A drink. You can add it to a drink so people drink the poison.
Now I did some thinking. Immune to poison... what is poison?
By definition: A substance that, when introduced into or absorbed by a living organism, causes death or injury, esp. one that kills by rapid action.
Well... high doses of lots of chemmicals will do that. Would you consider morphine a poison? Cause you can easily overdose on that and die.
So I am offically ruling that "Immune to Poison" for 1 PP refers ONLY to naturally occuring poisons. Such as a spider, or a snake venom.
Immune to "Chemicals" is 10 PP and treated like immune to "fire" And your poison can have descriptor "chemical" or "natural" depending on how you want to build your character.
Something you can do, is take expertise poison, and have Benifit "Apothacary"
This will allow you to be able to examine exsisting poisons, craft new ones like "devices" for a scene, or even craft antidotes for poisons.
You could also grab expertise herbology to synergize your poisons, and make the DC on things lower.
I dream of being the next Shakespear, Dickens, George R.R. Martian, or even J.K. Rowling... but then I look at my work and think... Dang.My Characters