Cleric

Clerics are religious mages, whose magic is granted to them by their god. Clerics serve their gods by spreading their good (or otherwise) word and increasing their influence in the material world.
Clerics are granted the ability to cast spells upon proving themselves worthy of it, and so most would-be clerics spend years in study and religious contemplation before ever gaining access to magic. Unlike wizards and druids, whose magic is taught, clerics do not need to fear the ravages of harnessing mana directly. However, because they are drawing upon their god's power, they can only cast a limited number of spells per day, whereas wizards and druids may cast an indefinite number (so long as it doesn't kill them).
Clerics, due to serving a god, are also held to a higher standard than a mere worshipper. In addition to daily religious rites and prayers, clerics must remain devout and behave within the disposition expectation their god lays out. Clerics must remain within 1 step of their god's alignment, as well, or else be stripped of their powers and magic. A fallen cleric must atone for their transgressions, though some will elect to abandon their god and serve one of its rivals. And for the most foolish, or desperate, some choose apostasy, leeching off of their former god's power. Those who become apostates can never be forgiven and will be struck down on sight, their souls doomed to a fate worse than death.

Pantheons

The gods of the New Faith, as well as other gods known on Earth, can be chosen as a cleric's divine patron.

Gods of Light: gods that mostly embody ideals and positive domains.

Gods of Twilight: gods that represent neutral aspects.

Gods of Darkness: gods of evil or undesirable domains.

The Cosmic Wardens: gods charged with overseeing Earth's mana temples

Other Gods: gods who have a presence and following on Earth but do not fall into one of the above pantheons

Classes

Chaplains, the default clerics
Divine Curates (Humans only), gains superior magic in exchange for deeper devotion
Divine Partisans (Satanai♂ only), militant servants of Yawey, who see all other faiths as blasphemy
Ecclesitheurges, clerics who sacrifice martial training and rely solely on their god's protection
Ex-Vicars, fallen paladin vicars who yet still revere their god, even if they no longer pursue their grand quest
False Wizards, clerics who pretend to be arcane mages for one reason or another
Friars, religious monks who train in martial arts alongside their religious studies

Recommended Prestige Classes

Bishops
Chosen Ones
Dragon Disciples
Living Legends
Pharaohs
Rusalka Lords
Vampire Lords