United in Stormwind Cards List & Guide
Hero PowerDiscard a random card.
From what I've seen on the boss encounter in wowhead. If you gain all of the brood affliction you transform into a dragonkin (of some kind), so I'm guessing this simply punishes you for ignoring the existing brood afflictions or not being able to dispose of them. Regardless, this hero power shouldn't be obtained if you manage your hand properly.