Blizzard has shown three of the 31 cards coming to Hearthstone's new Blackrock Mountain expansion. Everyone loves minions that summon other minions, right?
Each of the three revealed cards has a little lore to go with them, so the Grim Patron up there is built around the idea that dwarves love a good bar fight: "If you decide to throw the first punch, prepare yourself as a few grim patrons (and all of their friends) join in on the action!"
The Axe Flinger card on the other hand builds on the fact that "the heat of Blackrock Depths has forged the Dark Iron Dwarves into singe-proof juggernauts" that can take pain and dish it out.
And, lastly, there's the Lava Shock card, which means that "Shamans can harness the essence of lava in order to melt away their Overload problems."
[Blackrock Mountain – Delving into Blackrock Depths - battlenet.com]