The Spellplague was a magical disaster that struck Faerûn in 1385 DR when the goddess of magic Mystra was assassinated by the gods Cyric and Shar. During the ten-year period that followed, magic was unreliable; in some cases it had the opposite effect, had additional unintended effects, or affected others than the intended target; often the spellcaster would be immolated in blue flame, either unharmed, harmed, or killed by the fire; and in many cases, magic failed outright. Many magic items lost their power, but still others endured.
The long-term effects of the Spellplague on Faerûn resulted in areas called "plaguelands." In such places, the blue fires of the Spellplague had literally altered the terrain and left pockets of wild or dead magic. Some humanoid spellcasters or others who ventured too close to plaguelands were also physically altered, a state called "spellscarred." Spellscarred mages have survivable magical deformities, and some even learn to use these powers in battle. Those who were not so fortunate are called "plaguechanged," creatures mutated by the Spellplague into terrible abominations. The likelihood of becoming spellscarred or plaguechanged increases as one continues to use magic, or as one spends an increasing amount of time in a plagueland.
With the coming of the Spellplague, many magical nations were overrun by their enemies or fundamentally altered, politically and socially, if not physically. The kingdom of Cormyr, whose military might had long been supplemented by the King's elite War Wizards, is one such nation. Without access to their powerful magic and many of them missing or dead, political upheaval becomes increasingly likely as time passes and more and more War Wizards succumb to the Spellplague.