Spells
All spells in The Domains of Dread are subject to their type - in other words, their origin and font of power. Classes who share spell types also share spellbooks. Certain classes or archetypes may have unique spell-like abilities, but all spells are localized to spell type, not class. This is a major divergence from Third Edition rules where spellbooks are, broadly, specific to a spellcasting class.
Spell Types
Ancient
Ancient magic is derived from primeval, fundamental forces found in nature. The traditional custodians are Druids, but varieties of Hunters also find themselves aligned with the Cycle. The oldest form of supernatural power tapped by humanoids in most worlds with the Misty Plane, then, unlikely to be exempted from this wisdom.
Arcane
Arcane magic is derived from a force which stands in subversion of natural law. Practitioners may be born with influence over the arcane, as are Sorcerers, but more often come into mastery as part of lifelong study and application, like Wizards. Varieties of Hunters and Rogues, too, dabble in the arcane in pursuit of their goals.
Bardic
Speak the word and watch the world move. That is the power of bardic magic, tapping into powers hitherto pulled from diction and song. Though identified often with the arcane, bardic magic in practice is expressed through the particular whimsy of the individual, offering little heed to formula and rigid incantations. Bards are the namesake, however certain Berserkers develop similar aptitude for the song of battle itself.
Divine
Those who call upon a power greater than themselves, whether by invoking the name of a deity or greater ideoligion, draw from this font of potential be they through the lips of a Cleric or the Edicts of an Inquisitor. A Paladin's oaths, too, kindle this power from within - and there are Sorcerers who forsake their arcane talents in service of holy dogmas.
Occult
Perhaps the most mysterious force in the Realms of Terror, occult magic seems to manifest through not only supplication with outsiders, but the Mists themselves. It is then the hands of despotic intelligences and the wicked which most often come into this power but, as some Necromancers prove, occultism is not evil on its face, just as the Mists themselves are not. This does not curtail the fear and revulsion for such practices common almost everywhere in the Core, likening it to "black magic" as with Warlocks and Dark Knights. Some Rogues, meanwhile, demonstrate their abilities by paying fealty to the Dread Plane of Shadow.
Inherent
There is no spellbook associated with inherent powers. This is the domain of exceptional people whose abilities connect to a force found in all people such as the mind, like Psions, or the body and soul, like Ascetics.
Spell Schools
All spells in addition to alignment with a type are also subject to a spell school. These are notable in some cases, as with Wizards specializing in a spell school (except Divination), or specific consequences associated with certain spell schools around the Realms of Terror (evil Necromancy spells are, almost always, hated by a domain's society). A small number of spells are universal, belonging to no school.
Abjuration
Abjurations are protective spells. They may create magical barriers, negate the effects of other abilities, or bring harm to trespassers.
Conjuration
Conjurations involve the transport of an energy, thing or creature from another place, or the spontaneous manifestation thereof. In the Realms of Terror, no conjuration spell may bridge the Misty Border with another plane of existence as to call upon outsiders - only rituals. Neither is it possible for a spell to teleport a subject and certainly not over domain or planar borders.
Divination
Divinations are the determination of fate through magical means. The Mists conspire to choke all but the simplest organs of augury in their Realms of Terror. Those who seek this path anyway while not warded by the Vistani Sight may find themselves discovering that fate beyond the Misty Border is a question better left unanswered.
Enchantment
Enchantments affect the minds of others, influencing or controlling their behavior. All enchantments count as mind-affecting spells.
Evocation
Evocations bring something forth to then apply to another or an item, typically as a form of attack but not always. They may be rays, bolts or other expressions.
Illusion
Illusions seek to deceive or confabulate the senses. They may be phantom imagery, sounds or sensations.
Necromancy
Necromancies alter the status of a being's life or life force. Though many necromancies heal, others harm - and worse bestow the hollow facsimile of life in undeath.
Transmutation
Transmutations alters the nature, shape or aspect of a thing or creature.