Hey guys I bought expansion pass a while back,but now I also bought the Gwent deck and so now I got a copy of hearth of stone extra, Im selling it for 8 euros which is 2 less than the store offers,if you are interested message me :)

Selling game keys is not allowed here as per GOG staff's instructions.

www.gog.com/forum/general/gogs_general_trading_thread/post211

Though, you can still try trading it for other games in the trading thread linked above.