The closest thing Hearthstone has to multi-classing.
Thief Rogue (or Burgle Rogue) is a Rogue deck type which focuses on acquiring cards from other classes to augment their own. While most of these cards were used in various other Rogue decks, Thief Rogue as an archetype was pushed in The Witchwood with 
Tess Greymane and Spectral Cutlass, followed by Rise of Shadows. In the Year of the Dragon Standard, these decks rely on 
Underbelly Fence and Vendetta to push early game tempo, a powered up Spectral Cutlass for damage, healing, and board control, and Tess Greymane as a late-game finisher. Saviors of Uldum gave it a Quest card to go with it to make the archetype even stronger.
Thief Rogue loses a lot of impact when facing against other Rogues, since many abilities focus on cards from different classes.
Should a Thief Rogue steal a Hero card from another class, their Rogue cards will be considered "from a different class" instead.
Common cards
The following cards are usually in the deck.
Core cards
The following cards are played in most or all versions of the deck:
Optional Cards
The following cards are played more than occasionally, but not always:
Wild cards
This section concerns content exclusive to Wild format.Wild cards that fit well into this deck type:
