This week a new legendary card was revealed for Hearthstone - the Madam Goya from World of Warcraft Mist of Pandaria. Goya comes as the owner of the black market and she is going to Hearthstone as mysteriously as she appeared in WoW.
This card's Battlecry takes a friendly minion currently in the battlefield and shuffles it into the player's deck, then selects a different random minion from the player's deck and puts it directly into the battlefield.
Madam Goya's card effect is tricky to use and not reliable, but can be game-winning. The ideal outcome with Madam Goya is to target a low-cost minion and switch in a much stronger minion, preferably a minion with a strong end-of-turn effect like Y'Shaarj or ones with negative Battlecries like Deathwing. As a result, Madam Goya is best used in control decks with many high-cost minions. Since Paladins and Shamans can generate a minion with their Hero Powers, they possess the most convenient ways to generate targets for Madam Goya.
Madam Goya can also be used to return cards with strong Battlecries. However, using Madam Goya for this purpose is generally inferior to Youthful Brewmaster or Ancient Brewmaster since they can accomplish this more effectively while also having decent stats on their own.
Priests can use Madam Goya with temporary mind control effects to permanently take the minion for themselves (although this strategy is strictly inferior to Entomb in cost and card usage).
Video by Disguised Toast