StarCraft II is getting another expansion, titled Legacy of the Void, at some unannounced point in the future. To hold players over, developer Blizzard is making a free prologue for it.
Called Whispers of Oblivion, this prologue will have three missions, including the first focusing on Zeratul since the Wings of Liberty expansion. According to the developer, Whispers of Oblivion is meant to bridge the story gap between the last expansion, called Heart of the Swarm, and the upcoming Legacy of the Void.