The Weave
Mortals cannot directly shape raw magic. Instead, most who wield magic make use of the Weave. The Weave is the manifestation of raw magic, a kind of interface between the will of a spellcaster and the raw stuff of magic. Without the Weave, raw magic is locked away and inaccessible - an archmage can't light a candle in a dead magic zone. But, surrounded by the Weave, a spellcaster can shape lightning to blast her foes, transport herself hundreds of miles in the blink of an eye or even reverse death itself. All spells, magic items, spell-like abilities (such as a Blackguard's or Assassin's spells as presented in Neverwinter Nights 2), and even supernatural abilities such as a ghost's ability to walk through walls depend on the Weave and call upon it in different ways.The exact nature of the Weave is elusive, because it is many things simultaneously. The Weave is the body of Mystra, the goddess of magic. Mystra has dominion over all magic worked throughout Toril, but she cannot shut off the flow of magic altogether without ceasing to exist herself. The Weave is the conduit spellcasters use to channel magical energy for their spells, both arcane and divine. Finally, the Weave is the fabric of esoteric rules and formulas that comprises the Art (arcane spellcasting) and the Power (divine spellcasting). Everything from the texts of arcane spellbooks to the individual components of spells is part of the Weave. Magic not only flows from source to spellcaster though the Weave, but the Weave also gives spellcasters the tools they need to shape magic to their purposes.
Whenever a spell, spell-like ability, supernatural ability or magic item functions, the threads of the Weave intertwine, knit, warp, twist and fold to make the effect possible. When characters use divination spells such as detect magic, identify, or analyze dweomer, they glimpse the Weave. A spell such as dispel magic smooths the Weave, attempting to return it to its natural state. Spells such as antimagic field rearrange the Weave so that magic flows around, rather than through the area affected by the spell.
Areas where magic goes awry, such as wild magic zones and dead magic zones represent damage to the Weave.
NOTE: Most wild and dead magic zones on Toril formed during the Time of Troubles. As such during the current server time, such concepts are merely theoretical, discerned by intense study of wizards attempting to learn more about how the Weave functions.
Mystra has the ability to deny any creature the ability to access the Weave for as long as she chooses. This is a power rarely exerted, however, and she reserves it for those who seek to do damage to the Weave or magic itself (among those she counts anyone who chooses to access the Shadow Weave), as to do so she must spend time to discern the offender's location and proceed from there.
She cannot deny a god access to the Weave, but she can indirectly stop a deity from having an influence by shutting down their worshipers one by one. However, this is something she wouldn't do under normal circumstances for two reasons.
First, doing so would drive more people to take up use of the Shadow Weave.
Second, it would most likely upset Ao as the balance among the gods would shift dramatically.
"Open any three books describing the magic and mage lore of
Faerûn, and you’re apt to find three conflicting accounts of the
origins and true nature of magic. Some of this apparent contradiction
is deliberate falsehood designed to restrict the mastery of
magic to those beings properly trained. Much of the rest of it
arises from strange views or outright mistakes often unwittingly
reproduced by later scholars.
Hear now the truth of things, as best it is understood. To speak
simply, all known worlds and planes swarm with ever-present energies.
Large and small, free-flowing or bound by physical barriers or
magical effects (themselves merely energies shaped and designed to
restrict or hold other energies), these surges and dissipations of
energy give light and life and movement to everything. They are
the stuff of life itself, and they would be present even if all living
and once-living things on Toril were stripped away to bare rocks.
What some folk refer to as magic and wizards speak of as the
Art is the means by which some beings can call on the ever-present
energies and wield them to create effects. Sorcerers do this
instinctively through an innate gift and the incredible force of
their personalities. Bard songs waken echoes of the songs of beginning,
the music of creation itself. Wizards construct processes—
spells—enabling them to bend the Weave to their will in order to
do what they desire. The divine power infusing any cleric holding
the spells of her god or goddess can do the same, shaping the
Weave through the holy (or unholy) power granted her.
Many types of magic—rune magic, shadow magic (not to be
confused with the Shadow Weave), gem magic, elemental magic,
even the elven high magic of old—have been spoken of down the
years, but these are all merely different processes or paths to the
same mastery of natural energies. This endless, ever-shifting web
of forces is known as the Weave. Humans refer to the entity or
awareness that is bound to the Weave of Toril as Mystra, and worship
her as their goddess of magic.
The present Mystra is a recently ascended mortal woman, who
took over from her exhausted predecessor during the Time of
Troubles. Mystra exists to give magic to all creatures and to control
its use. In ancient times, the archmages of Netheril ignored
the dictates of Mystryl, goddess of magic at the time. One, the
wizard Karsus the Mad, tried to seize divinity by the casting of
mighty spells that would have wrecked Toril’s Weave. Mystryl sacrificed
herself to save the Weave. Her successor Mystra decreed
that no mortals would be allowed to wield such terrible magic
again—and that decree holds to this day.
Mystra wards the Weave against those powerful or reckless
enough to damage it further. Until the world changes or the
divine powers themselves lay down their guardianship over human
affairs, the high and perilous magic of the past remains locked
away under Mystra’s eye."
- Elminster (post Time of Troubles, so the "mortal woman remark isn't true).
Roleplaying Magic and the Weave
The simple truth in Toril is that all magic is worked through the Weave (almost; see the Shadow Weave below). To most learned spellcasters this is a widely accepted fact. The few who believe they have found another way of casting spells are plain wrong (or are Shadow Weave spellcasters, in which case they are right - sort of). Magic is a terribly powerful force to wield. What we can do in Neverwinter Nights 2 is merely a very combat-oriented fraction of its true extent, and as such all spellcasters - arcane or divine alike - are afforded a great deal of respect by the common people of the Forgotten Realms. The simple fact is that no one can discern the true power of a mage or priest without tempting their wrath - and this is a risk few are foolish enough to take.
However, what people don't understand they also frequently fear, and the common folk are likely to distrust or fear a mage (less so with more benevolent priests); but they are still not generally going to test your power.
Spellcasters are relatively uncommon, however. The Forgotten Realms Campaign Setting claims only about one out of a hundred have the mind or talent required to advance far in either the Art or Power. This ratio goes up somewhat among races which have favoured classes that are spellcasters (such as wizards among moon/sun elves or drow, and sorcerers among wild elves) to about one out of every ten.
The Shadow Weave
During the course of her eternal war with the goddess Selune, the godess Shar created the Shadow Weave in response to Selune's creation of Mystra and the birth of the Weave. If the Weave is a loose mesh permeating reality, the Shadow Weave is the pattern formed by the negative space between the Weave's strands. It provides an alternative conduit and methodology for casting spells.Shar, being the goddess of secrets, has mostly kept the secret of the Shadow Weave to herself. Over the millennia some mortals, mainly her servants, have been allowed to discover the Shadow Weave or have stumbled across it in their researches.
Shadow Weave users enjoy several advantages. First, they ignore disruptions in the Weave. A Shadow Weave effect works normally in a dead magic or wild magic zone (but not in an antimagic field). Skilled Shadow Weave users are able to cast spells that are extraordinarily difficult for Weave users to perceive, counter, or dispel.
Shadow Weave users also suffer some disadvantages. First, Shar has full control over the Shadow Weave and can isolate any creature from it or silence it entirely without any harm to herself. Second, the secrets of the Shadow Weave are disquieting and injurious to the mortal mind. Without assistance from Shar, a Shadow Weave user loses a bit of his or her mind. Third, while the Weave serves equally well for any kind of spell, the Shadow Weave is best for spells that sap life or muddle the mind and senses, and is less suited for spells that manipulate energy or matter (in game mechanics, this gives a Shadow Weave caster some benefits when casting Necromancy, Enchantment or Illusion spells, and penalties when casting Evocation and Transmutation spells). The Shadow Weave is also completely unable to perform spells that create light (such as the spells light, sunbeam and sunburst).
Finally, the more familiar a mortal becomes with the secrets of the Shadow Weave, the more divorced she becomes from the Weave. An accomplished Shadow Weave user can work spells that Weave users find difficult to detect, dispel or counter, but the Shadow Weave user also becomes similarly unable to affect spells worked through the Weave.
Roleplaying the Shadow Weave
At this point in our timeline, almost no one knows about the Shadow Weave. It is only after the Time of Troubles that the use of Shadow Magic becomes more known.You should not be roleplaying that your character knows about the Shadow Weave, unless he has discovered it through the course of a DM event. Those characters who somehow hear about the Shadow Weave should generally consider it an absurd rumor.
Roleplaying the USE of the Shadow Weave is godmodding, and should not be done without DM permission.