The Source
The bladder of the fang — the venom door's delivery, the serpent-folk distillers' own, and the one the world gives with an address.
The Yield
A fang gives a vial's worth; a vial's worth gives the address; the address is the one the hunter points.
In the Workshop
The bladder is the crossing made flesh: the venom is poison that has learned to aim, and the bladder is the one who carries the aim until the spell or the dart gives it an address.
Cost band: master (the reagent grade) — on the ladder in The Maker's Hand, the material is the floor, and the floor is the one the mine or the marsh or the tree has to give. Recipes that take it: distillation, the venom school's reagent spells