Hearthstoneis cooling off this summer with a wintery, death-themed expansion called Knights of the Frozen Throneinspired by the northern home of the undead Scourge, Northrend.

Blizzard revealed Hearthstone: Knights of the Frozen Thronelast night with a handful of new cards and a tease of what's to come in August: heroes turning into Death Knights with new hero cards and quests that send players through the Lich King's Ice Crown Citadel.

There are two major focuses in Knights of the Frozen Throne: the new effect Lifesteal and the new hero cards. The Lifesteal effect, which heals heroes for the equal amount of damage a card deals, will be popping up on minion and spell cards in the expansion, including these two new cards:

The hero cards coming in the expansion transforms the class heroes in the game into Death Knight versions of themselves, altering their hero powers and appearances for the rest of the game. The one hero card revealed is called Deathstalker Rexxar, which deals damage to enemy minions and transforms the hunter Rexxar into an agent of death.

Here's a look at some of the new cards in action, including Rexxar's Death Knight transformation:

New missions in Knights of the Frozen Thronewill have players battling against bosses from the Lich King's Icecrown Citadel, including the undead frost wyrm Sindragosa, Professor Putricide, Lady Deathwhisper, and the Lich King himself.

You can check out new cards as they are revealed between now and August here.