Hearthstone's new expansion is Kobolds and Catacombs, and has a new single player mode

Blizzard's fiesta of fun Blizzcon starts today, and that means announcements. One of the most exciting? The new Hearthstone expansion Kobolds and Catacombs, which game designer Ben Brode calls "our love letter to that classic, fantasy, dungeon crawling vibe."

We got to see a handful of new cards, like Dragon Soul that lets you summon a 5/5 dragon if you can cast three spells in a turn. Gather Your Party lets you recruit a minion from your deck, Crushing Walls destroys your opponent's left and right minions. 

The biggest news was a brand new single player mode that comes as part of the expansion, Dungeon Runs. Blizzard promises this mode will "send Hearthstone players on challenging, high-stakes subterranean adventures inspired by the classic fantasy dungeon crawl." You'' start with a novice deck and fight tougher and tougher boss battles, looting new cards for your deck along the way. Lose one battle though, and you have to start all over again.

The new expansion will launch in December, with 135 new cards. To celebrate the all players who log in to Hearthstone from Monday will get the card Marin The Fox for free. His powers? Marin The Fox will spawn a chest on the board. If you can break that chest open, you'll earn "one of the craziest cards we've ever made in Hearthstone," like Tolin's Goblet, which lets you draw a card and then fill your hand with copies of it. You can almost smell the rage quits from here.