Otherwise known as Evaluating Intelligence this is a lore skill related to magic.
This skill not only allows you to obtain information about the magic abilities of other beings, but it also increases the effects of spell cast such as duration of fields and power of damaging spells.
Mystic Lore also allows you to cast spells directly through scrolls, consuming no reagents and using only half the required mana.
To perform such action you must have the equivalent amount of skill in Mystic Lore as the amount of skill it takes in Magery to normally cast the spell. For example, to cast Flamestrike directly through scrolls you need 70% Mystic Lore.