Last week, Blizzard updated Hearthstone and enabled the use of Goblins vs Gnomes expansion cards within the arena, days before the initial release date. Blizzard's little tease also gave all players a free arena a ticket so everyone could get a taste of the new cards.
On Monday, Blizzard finally released the Goblins vs Gnomes expansion, adding 143 new cards along with new booster packs, which only include GvG cards. The expansion is free, but acquiring the new cards requires purchasing expert packs, either with real world currency or in-game gold.
Hearthstone is available to download for iPad, Windows, and Mac for free.