An Oblivion Potion will allow you to unlearn one of the professions you currently have. There are separate potions for each profession, sold by the main trainers of each respective profession for a price of 38 .
This can be used if you are unhappy with your current profession, or if you simply want to try something new. Drinking this potion will permanently remove all skill points that you might have gained in that profession. If you later change your mind (again), you'll have to train the profession from scratch.