Eternal Conflict is is a new promotion for Heroes of the Storm that will add new new characters to the game from the Diablo series, while adding a new battleground to the game.
"This is something the players have been asking for," Alan Dabiri, technical director on Heroes of the Storm, said in a previous press conference. "Up until now, we've had all these different battlegrounds, but they haven't been in our Blizzard universe. This is the first opportunity for players to see one of their favorite game worlds... and we'll keep doing that."
You can see the trailer for the event and new content above, and read more about what to expect.