Let’s keep card-battling our way up the mountain.

Blizzard has unleashed the fourth part of its latest add-on for Hearthstone: Heroes of Warcraft. Blackwing Lair is live now as part of the weekly release of new content from the Blackrock Mountain adventure. You can purchase access to this episode right now for $7 or 700 in-game gold pieces. Or you can buy all five wings at once for $25. Worldwide gaming revenues on mobile reached $30 billion in 2014, and Hearthstone is Blizzard’s attempt to capture some of that.

New content like this is one of the ways that Blizzard is keeping the free-to-play card feeling fresh for long-time players. The add-on doesn’t just give fans new stuff to do, but it also includes new cards that can give an advantage in online matches. So releases like this rile up excitement, stir up engagement, and encourage spending. All of that is important to keeping a mobile game thriving.

Blackrock Mountain is a single-player adventure mode for a game that is typically played online against other humans. As with the previous wings, Blackwing Lair introduces three new boss battles that will test your skills and creativity. Additionally, the new content includes special challenge stages that are specific to certain hero classes.

This is the third major add-on for Hearthstone. Blizzard has previously released another five-part adventure add-on called Curse of Naxxramas, which introduced a few dozen new cards. After that, Blizzard went ahead with a full expansion called Gnomes vs. Goblins that saw the release of more than 100 new cards. Unlike the adventure add-on, which give you cards for completing challenges, you can only get Gnomes vs. Goblins content by purchasing booster packs.

Next week will mark the final release of Blackrock Mountain and the end of Hearthstone’s latest growth spurt. Looking ahead, fans will likely spend the next few weeks discovering fun ways to use the new cards.