Spellplague

The Spellplague, called the Blue Breath of Change by the inhabitants of Returned Abeir, was a disaster that struck Realmspace, the world of Abeir, and even the planes themselves on Tarsakh 29 of the Year of Blue Fire, 1385 DR, and was caused by Mystra's assassination at the hands of Cyric and Shar. With the goddess's death, the Weave, the universal structure of arcane forces, convulsed. It continued for a decade, leading to the Wailing Years, during which arcane magic ceased to function and the planet of Toril was transformed.

The diviner Yaphyll had a vision of the event: ""The white queen is troubled but can't say why. The black queen hates the white and gives the assassin a black coat. The assassin steals upon the white queen. She can't see him gliding through the shadows. The sword screams. The white queen falls. Her city falls. Stones fall in the cavern to crush the soothsayer. The tree burns and thrashes in agony. Branches break. Branches twist and grow together...""

- from a vision by the diviner Yaphyll

In her vision, Yaphyll referred to Mystra as the white queen and to Shar, goddess of the night, as the black queen. Cyric, god of murder, was the assassin, Savras, the god of divination, was the soothsayer, and the city, cavern and tree symbolized the ordered structures of magic crumbling into chaos.

The breakdown of the Weave could be felt by all wizards across Faerûn.

Storm
The storm began over the Mhair Jungles west of Halruaa and quickly grew to a massive size, with blue flames visible in the sky. It laid waste to Halruaa due to the heavy wild magic activity in the area, and Sespech, the Golden Plains, and the Nagalands were transformed into an unpredictable and surreal place, dubbed the Plaguewrought Lands. Almost every part of Faerûn was affected by the Spellplague and certain areas were eliminated entirely, while others were created anew. Thousands of mages were either destroyed or went insane due to the collapse of the Weave after Mystra's death. Without the Weave, the Shadow Weave was unable to be maintained and collapsed as well. In Cormyr, a third of the War Wizards were either killed or driven mad. Those who survived were forced to learn martial combat as a result of the disappearance of arcane magic.

The blue flames infected even portals and planar gates, spreading even further across Toril. It was through those gates that the Spellplague traveled across time and space, and reached the world of Abeir. In that world, the Spellplague first appeared in Gontal, the southwestern region of the continent of Laerakond, were it made contact with the ancient fortress of the Primordial Nehushta. 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. Laerakond was torn apart in a powerful earthquake, and a portion of the nation of Skelkor, were the capital of the dragonborn nation of Tymanchebar was located, was torn asunder and disappeared amid the blue fire.

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, but actually Unther was instead transported to the world of Abeir. However, it was transported to the lands of Shyr, the equivalent continent to Faerûn in Abeir.

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.

Effects on arcane magic

 * Despite the efforts, with the structure of magic out of balance, many spells failed or produced unreliable results.


 * Most permanent magic items, such as artifacts, were left intact at the end of the Spellplague but charged magical items were either destroyed, warped, or simply ceased to function. Items with dormant magical qualities, which were manually activated, were largely unaffected by the Spellplague.


 * The Wards of Silverymoon were shattered.

Effects on the Gods

 * Savras died as a result of the dissolution of Mystra's home plane, Dweomerheart.


 * Azuth was thrown from Dweomerheart to the Nine Hells, where Asmodeus stole his divine essence, fused with Azuth, and became a god.


 * Dweomerheart itself was dissolved.


 * With his new found godly power, Asmodeus took advantage of the planar instability to hurl the Abyss to the Elemental Chaos in a attempt to end the Blood War. Asmodeus failed however, as throwing the Abyss into the Chaos didn't stop the Blood War, although it stalled it by a hundred years.


 * Cyric was tried by a conclave formed of Lathander, Sune and Tyr. They found him guilty of Mystra's murder and sentenced him to imprisonment in the Supreme Throne.


 * Lathander transformed back into Amaunator.


 * Nobanion tried to save a pride of lions in Gulthandor from oncoming blue fire. He came in contact with the blue fire, and it mutated him into a dark and bestial lion with a mane of blue flame.

Other effects

 * The Spellplague affected the landscape, making the ground rumble and heave up and down like the surface of the sea. Curtains of blue flame swept the landscape, reshaping the land by cutting crevasses or lifting and sculpting the plain into hills and ridges. Shards of earth wrenched themselves free and became earthmotes.


 * Waves of azure fires appeared everywhere, killing whatever they touched.


 * Rifts opened in the Underdark beneath the Sea of Fallen Stars, causing the level of water to drop, cutting many ports off from their livelihood and creating the Underchasm.


 * A surge in the use of technology, divine magic, and worship of the Deities of Knowledge and Invention.


 * Political upheaval across the land that resulted in many attempted coups, invasions, and uprisings. Especially against governments and nations that had relied heavily on arcane magic for defense or controlling their population.


 * In 1386 DR large parts of Abeir and Toril switched places (small, almost imperceptible parts had been switching places since the Time of Troubles but this event was markedly more noticeable). A portion of Shyr violently changed places with large sections of Chondath and western Chessenta. Displaced genasi quickly set about creating a kingdom of their own, Akanûl.


 * Southeast Chessenta was also obliterated by the creation of the Underchasm. Chessenta survived and prospered - though its beloved ruler Tchazzar disappeared without a trace.


 * Mulhorand was completely destroyed, and the Mulhorandi pantheon disappeared. The land was later settled by Deep Imaskari and became the empire of High Imaskar.


 * Chult became a large island when most of the Chultan Peninsula was cut off from the mainland. Much of Samarach was drowned, its survivors spellscarred, and the yuan-ti realm of Serpentes fell. The city of Mezro collapsed and its ruins became occupied by the undead remains of those who didn't make it out in time. Ubtao's barae were lost and the jungle became home to massive monsters from Abeir.


 * Evermeet was pushed into the plane of Faerie, leaving behind a pale shadow of what the island of the elves used to be, though the isle's residents could move back and forth from Faerie to Faerûn at will.


 * The island of Nimbral completely disappeared.


 * The Shaar became a wasteland called the Shaar Desolation.


 * The region surrounding the Great Rift became the Underchasm. Bits of what used to be the Underdark began to float above the Underchasm as earthmotes.


 * The halfling realm of Luiren was submerged underwater, becoming the Gulf of Luiren in the Great Sea. In the century since that great disaster, the waters receded, and stories told by travelers from the south told of halfling communities that survived as island redoubts.


 * Lantan was hit by massive waves and flooded, killing, as it was thought, all of its inhabitants.


 * The peninsula known as Var the Golden became a region of the Great Sea called Var the Drowned.


 * The Misty Vale was devastated by blue fire, though the wild elves that occupied it survived. Known as Elfharrow, it was fiercely defended from all intrusions.


 * The illusions that cloaked the settlements on Selûne failed, revealing them to those on Toril.

Aftermath
By 1395 DR, the majority of the effects of the Spellplague had come to an end and most arcane magic had returned to a semblance of normality, with a handful of major changes to the way spells are cast. The Empire of Netheril came across the Lost Vale and displaced the saurials there into the Underdark.

By 1479 DR, areas of Toril still affected by the Spellplague were referred to as Plaguelands.

By 1480 DR, the Spellplague had ended with the event known as Mystra's Return. The Weave was resurrected with the goddess and magic became what it was before the Spellplague, though some areas with lingering effects from it remained.

In 1482 DR Lord Ao began the Second Sundering, as a way to restore the worlds of Toril and Abeir of the ravages of the Spellplague.