A 076

Every attempt to produce a product for a purpose uses a Craft skill. Drow of the Underdark introduces the skill Craft (Poisonmaking) to create poisons (see page 46) and mentions harvesting body parts, but doesn't specify a skill for harvesting raw materials for poisonmaking. Absent RAW guidance, you'll have to talk to your DM about what specific Craft skill is necessary to harvest venom from a particular type of enemy, and then either use the existing Craft (Poisonmaking) DCs for turning the venom into a poison suitable for use outside that foe's body, or your DM will need to establish the DC for a new type of poison.