Take a look at this from Kotaku:
Blizzard has announced that this July it will release three missions that act as a prologue to Starcraft 2: Legacy of the Void. Whispers of Oblivion is a three-mission arc that tells the story of Zeratul, a character we’ve only met through Heroes of the Storm,Blizzard’s moba.
Zeratul was a main character in Starcraft: Brood War and in Starcraft 2 and both expansions. Zeratul has always been a very popular hero. A simple google check will easily identify this.
So fans are having fun with this. They’ve mocked Kotaku with their parody.
BTW, I now own ALL heroes in Heroes of the Storm. I think I bought the Nexus Pack and a couple of heroes that were on sale. Gold gain will get most of what you need.