Blizzard is teasing something new for Heroes of the Storm, and it's apparently an "outlandish" creature.
According to the tease posted on the official Facebook page for the game, this creature is responsible for the "missions minions" which have been found dead.
Heroes of the Storm players believe it to be StarCraft's Dehaka, due to footprints found at the scene.
Dehaka is a primal zerg pack leader from Zerus known for "collecting" living beings and taking their essence.
This would definitely explain the missing minions (being collected) and their deaths (essence sucked out). Plus, data mining from November 2015 pretty much confirmed Dehaka would be added at some point.
A new Balance Update will be released on Wednesday, March 16 which will adjust a number of heroes, abilities, and talents. It will be released in the Americas first, and will roll out to other regions throughout the rest of the day.
The update doesn't mention what was teased on Facebook. Surely we'll find out soon enough.