Being spread out into a diverse number of schools slows down your learning in each school. If you decide for certain that you don't want to finish off that Faren school that you started ages ago, then you may want to risk the negative side effects of a potion, in favor of long-term gain. It should be noted that, the more spells you are forgetting (in this case, the more Faren spells you have), the more likely something bad is going to happen.
Note: ALWAYS examine a potion before you quaff it. You can examine something before you buy it by right-clicking on it.
Forget Potions: I've lost Intellect Points! Is that a bug?
This is not a bug, nor is it a new effect. When you drink a forget potion, a few things can happen - all bad. You have a chance of forgetting a spell or skill not in the school you want to forget. You have a chance of having your links to the mana nodes severed. You have a chance of losing 3 permanent intellect points. Also (and this is for skill forgetting potions only), there is a chance that you will lose permanent health points. None of these things are bugs. Not everything that is bad that happens to your character is a bug. The moral of the story is don't drink forget potions unless you're sure that you want to drink forget potions. There are ample warnings associated with forget potions, warning of negative side effects.
Shal'ille
A Shal'ille forget potion can be purchased from Priestess Zuxana, after saying "potion of forgetfulness" to her, for 2500 shillings.
Qor
A Qor forget potion can be purchased from Priestess Xiana, after saying "potion of forgetfulness" to her, for 2500 shillings.
Weaponcraft
A Weaponcraft forget potion can be purchased from Priestess Qerti'nya, after saying "potion of forgetfulness" to her, for 2500 shillings.
Kraanan
A Kraanan forget potion can be purchased from Rook, after saying "potion of forgetfulness" to him, for 2500 shillings.
Riija
A Riija forget potion can be purchased from Zala Ix'mecya (shopkeeper on the island), after saying "potion of forgetfulness" to her, for 10,000 shillings.
Jala
A Jala forget potion can be purchased from Wulfgang, after saying "potion of forgetfulness" to him, for 20,000 shillings.