Origin Feat

Through some event in your past, you find yourself either more or less than humanoid.

More or Less: Choose a creature type other than your current one(s). In addition to your current creature types, you also become that type. 

Internal Understanding: You have advantage on Charisma (Persuasion), Charisma (Intimidation) and Charisma (Deception) checks made when interacting with creatures of the chosen type. In addition, you have advantage on Survival (Wisdom) checks made to track creatures of the given type, and Intelligence (Investigation) checks to investigate for activity related to the given creature type.

Familiar Stimuli: You are used to dealing with the tricks of the chosen creature type. When a creature of the chosen type forces you to make a Saving Throw and you fail, you may add your proficiency bonus to the Saving Throw, potentially changing it to a success. You may only do this a number of times equal to your half of your Proficiency Bonus (rounding down), regaining all uses on a Long Rest. 

You may take this feature multiple times, choosing a different creature type each time.