Long time not seen fellows!
Today Blizzard released the first addon for Hearthstone called "Curse of Naxxramas". It is completely Solo. The addon is parted in four wings. Every wing gets opened after one week and cost 700 ingame gold or a small amount of money. The first wing is FREE. You can get new cards and legendaries by defeating for wow-players well-known bosses.
The first wing will be free for only one month.If u were thinking about starting Hearthstone -> this could be the right time.
more relevant information:curse-of-naxxramas™-wing-entry-details-and-heroic-mode-7-8-2014add apo#2820