Ubisoft has confirmed that Might & Magic Heroes VI Shades of Darkness, the add-on for their turn-based strategy, is going to arrive on February 28, 2013.

Here's more info:

The Shadow-tainted Dark Elves, a persecuted people, exiled from their homeland, torn apart by internal strife. As heir to the throne of Queen Tuihdana, the hero Raelag can unite them and make them rise again as a proud and strong nation. Forging an alliance with the powers of Darkness, he will get the support of the almighty Black Dragons and elevate the Dark Elves as masters of deception, stealth and assassination!

The Necromancers of Heresh face a crisis that threatens their very existence as a magical disease is slowly destroying their Spider Goddess, the Mother Namtaru. The player will incarnate the vampire hero, Vein, a rogue Death Knight with a troubled past. After allying with a former mentor, Vein will discover the source of the disease is connected to the Dark Elves and the infamous Netherlord, Sandro. To thwart Sandro's plans, Vein will have to repair the corrupted memories of the Mother Namtaru and restore her godlike powers.

There's also the Might & Magic Heroes VI Complete Edition, which offers a "fully-enhanced version of the game, all bonus maps & items, two adventure DLC packs, the original soundtrack of the game and the Shades of Darkness expansion."