While the concept of wizard specializations along the classically recognized schools of magic certainly dates back to the time of Azlant—and perhaps beyond, into the dim recesses of time before humanity rose to prominence—it was the runelords of Thassilon who explored school specialization to its full extreme.
Focusing their research on the discovery that each school of magic was opposed by two specific opposition schools, the runelords developed methods of further enhancing their mastery over their chosen arcane specialties. Essentially, they defined these seven schools as much by what they couldn't do as by what they could. By excising “impurities” introduced by fixed oppositional schools, they traded arcane versatility for greater strength in their chosen fields. The seven schools of Thassilonian magic are presented above.
Only wizards can truly follow the ancient philosophies created by Thassilon's runelords. The choice to specialize in a Thassilonian school of magic must be made when a character first becomes a wizard. Once the choice to do so is made, it cannot be changed.
Benefits: A Thassilonian specialist wizard receives two additional spell slots of each spell level he can cast. These bonus spell slots must both be used to prepare the same spell from the wizard's school of specialization, allowing the wizard to cast that spell twice (as he has prepared the spell twice). The wizard cannot use these slots to prepare two different spells, even if they are of the school he is specialized in.
Restrictions: A Thassilonian specialist does not get to customize his choice for opposition schools—his opposition schools are determined for him when he chooses his specialization. These restrictions are more significant than those most wizards follow, and are known as prohibited schools. A Thassilonian wizard can never prepare a spell that is in one of his prohibited schools—he treats these spells as if they were not on the wizard spell list. If using a spell trigger or spell completion item to cast a spell from one of his prohibited schools, he must use the Use Magic Device skill to do so.
Sin mages who follow the path of Envy focus on suppressing magic other than their own.
Sin mages who follow the path of Gluttony seek to manipulate their bodies in their unending hunger for life.
Sin mages who follow the path of Greed delight in transforming things into other things, as well as enhancing themselves.
Sin mages who follow the path of Lust gain great personal satisfaction at manipulating others' minds, emotions, and wills.
Sin mages who follow the path of Pride seek to perfect their own appearance and domain through trickery and illusions.
Sin mages who follow the path of Sloth enlist agents and minions to perform their tasks, or create what is needed as it is needed.
Sin mages who follow the path of Wrath focus on complete mastery of the raw destructive power of magic, and delight in channeling those destructive forces in awesome displays.