For those not familiar with the Pathfinder Role-Playing Game, anyone who belongs to the major races and is not a monster has class levels. However, there are no 0-level humans in the game like in earlier Editions. Instead, there are five NPC Classes meant to broadly cover the non-adventuring common folk of the realm. The Aristocrat is the rich noble who doesn't know much in the way of fighting; the Commoner is the peasant or unskilled laborer; the Expert represents a skilled tradesman; and the Warrior a common soldier who knows how to fight but does not approach the level of the Fighter (a master of war). The Adept is the sole spellcasting NPC class, yet surprisingly it only covers a narrow purview: the folk shaman living away from civilization who gains minor spells from a patron. Given its limited spell list and the differing game mechanics for magical traditions, the Adept can't really reflect the studious hedge mage, cunning illusionist trickster, or other minor apprentices common in magic school campaigns and Sword & Sorcery demonic cults.
By sheer chance I stumbled across an interesting Variant Adept within a free adventure for the Scarred Lands Campaign Setting. Basically, it allows the Adept to expand their spell list to a small selection of ones from PC classes, and to trade in their Familiar class feature for another supernatural boon. That way, a DM can have adepts who are wizardly apprentices, followers of a druidic faith, or even cultists to a vile god. As this section of the rules in the adventure is designated as Open Game Content, I'm going to post it here in its entirety.
Optional Rule: Variant Adepts
These variant rules can make the adept NPC class much more versatile, representing anything from a simple apprentice wizard to a strange prophet, or even a druidic cultist who worships some primordial titanic power.
Spellcasting: An adept can cast either arcane or divine spells (choose one; this cannot be changed once decided), which are drawn from the adept spell list in either case. Like a cleric or wizard, an adept must choose and prepare her spells in advance. An adept cannot spontaneously cast cure or inflict spells.
To prepare or cast a spell, an arcane adept must have an Intelligence or Charisma score equal to at least 10 + the spell level. The Difficulty Class for a saving throw against an adept’s spell is 10 + the spell level + the adept’s Intelligence or Charisma modifier.
A divine adept must have a Wisdom or Charisma score equal to at least 10 + the spell level. The Difficulty Class for a saving throw against an adept’s spell is 10 + the spell level + the adept’s Wisdom or Charisma modifier.
Arcane adepts acquire their spells from books or scrolls and prepare them through study. The arcane adept keeps a spellbook just like a wizard, and uses it in exactly the same way that a wizard does.
Divine adepts must meditate or pray for their spells, in the fashion of a cleric or druid.
Where the adept class table indicates that the adept gets 0 spells per day of a given spell level, he gains only the bonus spells he would be entitled to based on his Intelligence, Wisdom, or Charisma score for that spell level.
Adept Talent: At 2nd level, an adept can choose any one of the following options:
Arcane bond: As the wizard class feature of the same name (either a familiar or a bonded object).
Bloodline: As the sorcerer class feature of the same name. She gains the bloodline arcana and bloodline powers for that bloodline as a sorcerer of the same level, along with any bonus skills. The adept may add the bonus spells for that bloodline to her spell list, but does not gain the bloodline’s bonus feats.
Cleric domain: As appropriate for the adept’s god, philosophy, or religion; she gains a bonus domain spell of each level she can cast, as a cleric, along with any domain powers. She uses her adept level as her cleric level for this purpose.
Nature bond: As the druid class feature of the same name. If she chooses an animal companion, the adept treats her druid level as half her adept level for that purpose; if she chooses a cleric domain, she gains a bonus domain spell of each level she can cast, along with any domain powers. She uses her adept level as her druid level for this purpose.
This ability replaces summon familiar.
Favored Class Benefit: At 1st level, the adept may choose cleric, druid, or sorcerer/wizard; once chosen, this class cannot be changed. For each favored class level in adept, the adept can effectively add one spell of any level she can cast from the chosen class’s spell list to the adept spell list.
You might notice that while the Variant Adept draws various abilities from the major spellcasting classes of Pathfinder, they are neither as powerful nor as versatile as the magical traditions they're meant to emulate. The ability to add more spells to the base Adept list (which is quite small in Pathfinder) only comes via a Favored Class Benefit, meaning that only races which have Favored Class: Any will be adding things like fireball, silent image, and third party spells to their repertoire.
I also find it interesting in how an arcane adept is not limited by an arcane spell failure chance, and thus can potentially cast spells in plate mail with the expenditure of feats. There's also no restriction in the text for a divine adept drawing Favored Class spells from the sorcerer/wizard list, or for an arcane adept to do the same with cleric/druid spells. Although the base Adept was a strong contender for being the most powerful and versatile NPC class, the variant version makes it good enough to be on par with some lower-tier PC classes.
The utility of a spellbook and allowing others to copy spells from it might present a potential problem in regards to the Leadership feat and followers. Even though the rules prevent a wizard from copying spells not on his class skill list into his spellbook (see "Adding Spells to a Wizard's Spellbook"), this can end up as a way for said PC to exponentially gain more spells for free. Adepts copying spells from PC class spellbooks is not as much of a problem, in that they only gain cleric/druid/wizard spells not on the Adept list via Favored Class, and thus only 1 per level at most.
Use in a Magic School Campaign
The variant adept is a good way to populate your academy with low-level student NPCs without worrying about class features, at-will cantrips, and the like. The adept's poor base attack bonus, lack of any martial weapon or armor proficiency, and low Hit Die and skill list make its minor spells and adept talent its sole strong suit. This archetype is perfect for the mass of fresh-faced youngsters dedicating their school months to study, and having all Knowledge skills as class skills for this last part doesn't hurt either!