While it has not been confirmed to be real yet, a French Hearthstone player has encountered an advertisement for the upcoming Knights of the Frozen Throne. In it, Jaina, Frost Lich is supposedly revealed in its entirety. While we've included the screen grab below, the actual tweet contains video of the ad which looks awfully convincing. Thus far the post has remained on Reddit, unconvincing fakes are usually downvoted and swiftly removed.
We will not be adding leaked cards to our database until someone from Blizzard confirms they are real.
If this leak is true, Uther and Gul'Dan will cost 9 and 10 mana, respectively.
The card's art may not match up to what we saw in the trailer, but she does somewhat resemble what we've seen from the key art where she's also wearing a dragon skull pauldron and the jeweled crown. You can find that image at the bottom of this post.
Note: This card may be fake. Take it with a grain of salt.
Update: CelestialSinn of Team Celestial in China tells us that there's been a leak for Jaina's hero card in China too. But theirs is about the hero power which reportedly acquires an added freeze effect.