Raid Boss Onyxia
Rush. Immune while you control a Whelp. Battlecry: Summon six 2/1 Whelps with Rush.
Onyxia chose her guises to manipulate mortals, but her true form? That was reserved for ending them.
Battlecry - Does something when you play it from your hand.
Immune - Immune characters can't be damaged.
Rush - Can attack minions immediately.