In a special stream on Thursday afternoon, the Hearthstone development team unveiled the upcoming expansion coming on August 3 and what players can expect alongside it.

Titled "United in Stormwind," players will kick back and relax in the famous Alliance city to the tune of 135 new cards. Unique mechanics, keywords, and content were announced as well.

https://www.youtube.com/watch?v=E0OfUJcBW_0

Tradeable acts as the expansion-specific keyword which allows certain cards to be played for their initial cost or they can be traded back into a player's deck for the cost of one gold. Once traded, a new card is drawn but the tradeable card's effect is not activated.

An example of one revealed on stream:

Mounts, Profession Tools, and Questlines made their debut as well on the official reveal stream as well. Each offers playing experiences that open up deckbuilding and strategies never seen before in the game's history.

Mounts act as spells that can be cast on minions and, when they die, the mount is summoned with stats and keywords equal to those on the spell itself.

An example of one revealed on stream:

Profession Tools act as weapons that do not have attack values but offer unique class-specific effects that reduce the weapon's durability. Paladin's Prismatic Jewel Kit, a weapon shown on stream, boosts the power of minions in your hand whenever a friend minion loses a Divine Shield.

Another example of one revealed on stream:

The final card type revealed was Questlines. Acting similarly to Quests of the past, these Questlines feature three different quests that need to be completed to further advance the story of one of the classes Mercenaries. Players start the game with the Questline in their hands and complete the steps to earn a small reward. Once all are done, the Legendary Mercenary minion is created in hand which has a powerful ability.

Mage's progress as follows:

More information about the expansion, as well as balance and cosmetic changes coming to Hearthstone Battlegrounds can be found here as the release date nears.