Dealings of the Dark Mistress
Nearly a century ago, Faerûn was ripped apart by an unfettering of wild magic now known as the Spellplague. Although sages and clerics might argue about the origin of the Spellplague, the effect was apparent to all. Huge swaths of the landscape were rent asunder. Entire nations were drowned, and large regions collapsed into the Underdark or were thrust up as spires of stone. The land became far more magical and fantastic in appearance, with islands of rock called earthmotes floating in the sky. The Spellplague infected everything: flesh, stone, magic, space and dimensional walls, and even the cosmology.
Another effect of the Spellplague was to breach the barrier between the twin worlds of Abeir and Toril. Portions of Abeir and Toril were swapped, leaving pockets of Abeir scattered across Faerûn. To the west, the entire continent of Maztica vanished, replaced by a new continent that many call Returned Abeir.
Although the Spellplague has largely run its course, its legacy lingers. Most creatures warped by the Spellplague have since died (of old age, sickness, or violent death), but a few, known as the plaguechanged, survive. Enduring pockets of unrestrained wild magic, known as plaguelands, lie scattered across Faerûn. Those who visit such areas and survive exhibit physical marks known as spellscars and often manifest bizarre abilities.