According to Blizzard’s description, “The Lich King’s entrepreneurial ventures in the mortal world are at an end, but you can now face him in Hearthstone! He’s brought all the terrifying power of the Scourge to the tavern, and each of Hearthstone’s nine classic heroes is poised to embrace the Lich King’s dark power to serve him as a Legendary Death Knight Hero card!”
The Knights of the Frozen Throne is the latest expansion for Hearthstone and will see the introduction of over 100 new cards to the game, thus expanding the player’s choices and ability to craft new decks. There will also be new heroes and new mechanics to help shake things up a bit.
The expansion is free to play, but access to the new cards comes in the form of booster packs which you can either try to earn by playing games, or spending real-life money to purchase them directly.