Heroes of the Storm is a free to play Blizzard brawler that is out now on PC and Mac and if you want to unlock the hero pack you should head over and check it out!
http://us.battle.net/heroes/en/heroes20/megabundles/
If you are curious to learn more about what Heroes of the Storm is Blizzard has a nice page dedicated to teaching the games core concepts you might be interested in.
http://us.battle.net/heroes/en/blog/20720242
