StarCraft 2: Legacy of the Void prologue available today
StarCraft 2: Whispers of Oblivion can now be yours.
StarCraft 2: Whispers of Oblivion is a three-mission prologue campaign for Legacy of the Void, serving both as a story bridge and a jumping on point for those who haven't kept up with the StarCraft saga so far. It features the Dark Templar Zeratul, apparently.
Although it will eventually be free to everyone, you can get your hands on it right now if you've pre-ordered Legacy of the Void through Battle.net. Legacy of the Void is expected before the end of the year, and pre-purchase also includes access to the beta when that kicks off.
If you're not yet a StarCraft player and are thinking of giving it a go, note that Legacy of the Void is a standalone release, so you don't need to pick up Wings of Liberty and Heart of the Swarm. Heart of the Swarm has itself just gone standalone, by the way, if you'd prefer not to wait.