I don't play Hearthstone (Gwent is my poison) and I got this from Diablo 3 battle chest I bought the other day so obviously this is a first come first served deal
Hearthstone - How to buy cards (buying and opening 7 packs) - YouTube
Dave Wilson på Twitter: "Happy Hearthstone patch day! I capped out on these free pack codes forever ago, but maybe you haven't. Fly, you fools! https://t.co/Ir9hotQnIY" / Twitter