The Hero is the main card in the deck.

A valid deck contains exactly one Hero card and a minimum of 39 or more (on Rated games) compatible non-Hero cards..
They must either belong to your hero's faction, either Human or Shadow; their class, either Warrior, Mage, Hunter, Priest, Wulven, Rogue or Elemental; or be Neutral. For example, if you chose Gravebone as your hero, then you may only add cards from the Shadow faction, the Mage class, or those denoted as Neutral to your deck.

Once its life reach 0, the player who controls the Hero lost the game.
Heroes, like allies, can be poisoned, disabled, set ablaze and Frozen.

There are currently 34 legal Heroes to choose from in Shadow Era (Carmila is a restricted promotional card only).
17 are Human and 17 are Shadow.