The last wing for the "Hearthstone: Blackrock Mountain" adventure is finally unveiled.

Dubbed as the "Hidden Laboratory", the fifth and final wing for this single player expansion has been released, featuring new rewards and four new boss fights.

First among the bosses is the Omnotron Defense System, with a skill that activates hero power via a Tron minion. There are four hero skills for this boss, namely: Arcanotron, where both players receive spell damage; Toxitron, dealing 1 damage to all other minions; Electron, reduces spell casting by 3; and Magmatron, where players who deals a card receives 2 damage. When players cast out the Omnotron Defense System, they can receive the Volcanic Drake card.

Meanwhile, also part of the "Hidden Laboratory" pack is Maloriak, with a passive Alchemist skill that swaps its attack and health whenever a minion is summoned by the player. The reward for conquering Maloriak is a Blackwing Corruptor, with Battlecry skill that adds 3 damages to a dragon card.

Third in the line is Atramedes, with Echolocate that consumes 1 mana. This skill equips a weapon that keeps on growing as the opponent deals cards, and the reward for this turn is a Drakonid Crusher with Battlecry that gains +3/+3 if the opponent has less than 15 health.

Finally, Nefarian makes a comeback in the final boss fight, with fire attacks that rain from above, and summoning two Bone Constructs in turn. When defeated, the turn rewards players with Dragonkin Sorcerer, adding +1/+1 for gamers that target this minion.

When players conquer all bosses from the "Hidden Laboratory", they will earn the Legendary minion Nefarian. This minion is an 8/8 one and costs 9 mana.

Additionally, the new wing also has a specific challenge for Paladins. Those who defeat the first boss, Omnotron, with a certain Paladin deck will earn the Solemn Vigil card, a 5-mana class spell that lets players draw two cards.