The Fall of Lordaeron

Prince Arthas Menethil, a young paladin of the Silver Hand, set out with the sorceress Jaina Proudmoore to stop the plague. At Stratholme he found the city's grain already tainted and ordered its people slain before they could rise as undead. Uther and Jaina refused to follow him. Arthas pursued the dreadlord Mal'Ganis to Northrend, burned his own ships so his men could not leave, and claimed the runeblade Frostmourne. The sword took his soul.

Arthas came home as a death knight of the Lich King and murdered his father, King Terenas, in his own throne room. The Scourge swept over Lordaeron. Uther fell defending the urn that held Terenas' ashes, and Arthas led his army into Quel'Thalas, broke the elves' defenses and used the Sunwell to raise Kel'Thuzad as a lich. Sylvanas Windrunner, ranger-general of Silvermoon, died fighting him and was raised as a banshee.

Kel'Thuzad then summoned the demon lord Archimonde in Dalaran, and the Burning Legion returned to Azeroth. Dalaran was smashed, and Lordaeron, the greatest human kingdom, was gone. In the north only scattered survivors, refugees and zealots remained, while Arthas's undead held the land.