“In Knights of the Frozen Throne, journey to Icecrown Citadel and experience:
135 new cards
Legendary Hero Cards – when played, transforms our nine heroes into fearsome Death Knights and gives players modified hero powers.
Eight free missions – fight epic bosses and a final showdown against the Lich King himself. Reward: get a free legendary card from completing the prologue and earn a card pack for each completed wing.
Lifesteal – new keyword and strength that heals players for damage dealt.”
Check out the video down below.
Source: Press release