You can read all details for the upcoming event, as well as the PTR Patch notes, on the official blog post.
King of Blades Arthas
Corrupted by the Zerg’s insatiable bloodlust, Arthas turns battlefields to burial grounds as the King of Blades.
Emperor of the Dominion Anduin
“The path to peace is through our children”, Anduin remarked, explaining the hereditary dynasty he’d made of the Pan-Terran Alliance.
Draenei Executor Artanis
Long-exiled by his adopted Nathrezim brethren, Artanis has finally found a new unity.
Mei has dedicated her life’s work in climate science to save the world for future generations. But if she can solve death, she can save everything.
Mineral Harvester Gazlowe
In the rear, with the gear… and a whole lot of explosives, ha!