Traveling Sisterhood of the Eternal Bants
After Mystra was killed, the Weave, the universal structure of arcane forces, was destroyed. Shar, opened a portal to the Far Realm in Dweomerheart, Mystras centre of power in the planes, seeking to destroy it, believing that she could control the Weave after destroying the plane of her former enemy. Without the Weave, Shar's Shadow Weave was unable to be maintained and collapsed as well. The breakdown of the Weave was felt by all wizards across Faerun.
The corrupted madness of Cyric defiled what arcane forces remained from the dissolution of the Weave, resulting in a new magical source of defiling arcane energy in the form of blue flames, that destroyed Dweomerheart and continued to spread across the multiverse.27
The Spellplague manifested in Toril as a storm of blue flames in the Mhair Jungles, west of Halruaa, and quickly grew to a massive size.4 Halruaan wizards, having divined the death of Mystra and the destruction of the Weave, were able to use the energy of the blue fire to save most of their kingdom by shifting it into another world, Abeir.8 However, the remaining Halruaan lands in Toril were laid to waste due to the heavy wild magicactivity in the area, and Sespech, the Golden Plains, and the Nagalands were transformed into an unpredictable and surreal place, dubbed the Plaguewrought Lands.2
The blue flames also infected portals and planar gates, spreading even further across Toril.2 Almost every part of Faerûn was affected by the Spellplague and certain areas were eliminated entirely, while others were created anew. Thousands of spellcasters were either destroyed or went insane due to the collapse of the Weave after Mystra's death.4 In Cormyr, a third of the War Wizards were either killed or driven mad. Those who survived lost their ability to use arcane magic.4 Other continents, such as Kara-Tur and Osse, were affected by the Spellplague as well.9
It was through the planar gates that the Spellplague traveled across time and space, and reached the world of Abeir.2 In that world, the Spellplague first appeared in Gontal, the southwestern region of the continent of Laerakond, where it made contact with ancient Glaur, the fortress of the Primordial Nehushta.1011 The fortress detonated when the "Blue Breath of Change" ran through it, in an explosion as potent as the Tearfall, rocking the entire planet of Abeir and creating the Glaur Barrens where the old fortress once stood.11 Laerakond was torn apart in a powerful earthquake, and a portion of the nation of Skelkor, where the capital of the dragonbornnation of Tymanchebar was located, was torn asunder and disappeared amid the blue fire.12
That region, where the city-citadel of Djerad Thymar was located, crashed on Unther, still enveloped in the blue flames. Many believed the Untherites and the Mulhorandi occupation forces were obliterated in the explosion that created the Black Ash Plain,13 but actually Unther was instead transported to the world of Abeir.14However, it was transported to the lands of Shyr, the equivalent continent to Faerûn in Abeir.15
The rest of Laerakond was sent to the Trackless Sea, were it subsumed the lands of Maztica. Maztica was transported to Abeir, and Laerakond, which became known as 'Returned Abeir', remained on Toril.16