In the words of Thrull, "Wizards are what all Mages should have been."
Wizards are mystically stronger than the Mages, but physically weaker. They get
more mana and their spells are more effective, but they also get lower
hp gains and are, at best, unimpressive in melee combat. They can also
learn some very rare spells by researching them from obscure spellbooks.
These spells are not listed on their skill lists.
This is a Prestige Classes for Mages, and they retain the original class's Prime Requisite,
in this case, Intelligence. Wizards cannot become Sorcerors. They disdain
what they see as the Sorceror's crutch-like dependence on the Dark Powers.