This is the Krul the Unshackled HS Legendary Warlock Card from the upcoming expansion Mean Streets of Gadgetzan.
It’s a Warlock class legendary minion and the card text reads: Battlecry: If your deck has no duplicates, summon all Demons from your hand.
You can get Krul the Unshackled by opening packs from the Mean Streets of Gadgetzan set.