Lore Spotlight: A Recap of the Shadowlands Story Up to Eternity's End

wowhead.com:

Patch 9.2 of the Shadowlands sees us heading to the new realm of Zereth Mortis, where we will learn all sorts of things about the First Ones and the nature of the Shadowlands itself, while preparing to face the Jailer in the Sepulcher of the First Ones, Patch 9.2's raid. But how did we get here? What is the story so far?

In the Shadowlands cinematic trailer, Sylvanas Windrunner made a move many had been dreading for a long time — she attacked the Lich King, Highlord Bolvar Fordragon — and took the Helm of Domination from him. Then she did something surprising. Instead of placing the helm on her own head, she tore it apart — and in doing so, tore a rift through reality itself, opening the way from the mortal realm of Azeroth into the Shadowlands, the realm of Death. But the story of the Shadowlands really began when Sylvanas, now working with her new mysterious allies in the Shadowlands, sent powerful winged creatures to kidnap some of Azeroth's most renowned heroes and leaders: Lady Jaina Proudmoore, Baine Bloodhoof, Thrall, and Anduin Wrynn — along with a failed attempted kidnapping of Tyrande Whisperwind. The Shadowlands pre-patch saw us dealing with the aftermath of these events — now that Bolvar no longer wore the Helm of Domination, he could no longer keep the Scourge in check, and they began to run rampant all over Azeroth. In the panic and chaos that followed, Taelia Fordragon learned for the first time that her father, Bolvar, had not died in Icecrown as she had always been told, but that he had become the Lich King. The way she learned this bombshell of information was… less than ideal. Mathias Shaw, spymaster and leader of SI:7, Stormwind's secret service, let it slip by