The alchemist can create special poisons that are more effective against certain creatures.
When crafting a poison, the alchemist can choose a single creature type (and subtype, if appropriate) from the ranger’s favored enemy list. Against creatures of the chosen type, the poison’s saving throw DC is increased by 4. Against all other creatures, it is reduced by 2. The alchemist must choose the creature type and subtype (if appropriate) while crafting the poison and afterward cannot change this choice.
Pathfinder Player Companion: Potions & Poisons © 2017, Paizo Inc.; Authors: Kate Baker, Eleanor Ferron, Nathan King, Lyz Liddell, Luis Loza, Alex Putnam, Alex Riggs, and David Schwartz.