Q 048

On the subject of Spell Mastery, another question, linked to the definition of "spells you already know".

From what I've read of the Arcane Magical Writings, a wizard "know" a spell when it is written is his spellbook and he can cast it. However, he doesn't need to have access to said spellbook - in fact, it is mentioned that a wizard can use borrowed spellbooks to prepare spell he knows in order to reconstitute a lost spellbook.

Thus, can a wizard (or other spellcaster preparing spells the same way) take the Spell Mastery feat while not having any access to his spellbook(s), and thus retrieve a few of his lost spells?


Q 049
Is there a definition in the game for "foes"?

Some spells specifically affect only the foes (or only the allies) of the caster, but does it depends on his perception of creatures as such?

For example, if a person pretend to be an ally, but is in fact just waiting the right time to backstab the caster, can he accidentally be affected too by a spell targeting foes?