Void Magic

Before there was the world -- before there was anything -- there was only the Void. Arcane magic functions by manipulating the Void, which represents what lies between two planes of existence. When a wizard opens a portal to the Lower Planes from his laboratory in Ralindor, each plane is like a room separated by a door, but the Void is like a hall. It exists independent of space and time; it cannot be seen, or touched, or visited, and yet arcane magic, from the smallest effect of prestidigitation to mighty spells like time stop, use the power of the Void to violate reality enough to cause miracles to occur.

Side/Secondary Effects

Prolonged instances of magic can render a place, such as a wizard's laboratory or sanctum, sensitive to the energy of the Void. It can tear open holes in reality, causing the horrible "creatures" within to leak out into the material world. But since they lack a physical presence in their home, when they arrive here, they violently scream into being as an un-reasoned mass of flesh with an alien mind. They are madness made physical. The most powerful of these creatures are the inscrutable Elder Gods, and the use of magic has brought the races of the world to their attention. They are not angry or jealous -- after all, would a man be angry or jealous of an insect? Rather, they see the constraining structure of time and space as a precious commodity they lack in the Void, and wish to break into the material world and warm themselves by the fires of reality. But without those constraints, their knowledge is omnipotent -- but interacting with the Elder Gods of the Void is sure to invite madness upon any scholar or spell-caster foolish enough to try to plumb the secrets of their home-dimension.

Manifestation

The Void allows people to access the powerful energy associated with other planes of existence, each of which is associated with powerful magical forces and energy. For example, when a sorcerer throws a fireball, he has used his magical prowess to briefly tap into the Roiling Chaos to steal enough elemental energy to cast the spell, while a warlock can access the Court of Fey to enchant a target with charm person.

Source

There are essentially three ways in which to gain access to the Void:

• Casters who study, including the bookish wizard, have tapped into gestures and incantations with their own inherently magical properties. By memorizing these patterns, they are capable of accessing the Void through pure training and knowledge. This art was brought to the Free Kingdoms by the elves. It also brings with it the greatest risk of destroying one's sanity, by delving into lore man was not meant to know.

• Natural spell-casters are already attuned to certain planes of existence. A spell-caster might have some broader connection to the Roiling Chaos or the Vale of Shadows might allow a spell-caster to throw lightning or turn invisible, while draconic ancestry grants someone with a modicum of the godlike powers of ancient dragons. They do not need to study in the same way wizards do; they have a foot in the proverbial door that leads into the Void.

• The third way to access magic is by forging pacts with creatures with their own magical essence; creatures with a strong connection to a magical plane, or those who, like sorcerers, are already connected to the Void. These warlocks, in exchange for services, are imbued with their own limited abilities to manipulate reality. Examples of such creatures include angels, demons, hags, or a plethora of other entities.