There is only one way to harm the demon lord and his minions. A weapon of power must be forged bearing his true name. When such a weapon is forged, the demon and all under his command are vulnerable. A lesser deity resides in Azshara: Lord Arkkoroc. You must seek him out but be warned, his minions will stop at nothing to destroy you if you are discovered. Undoubtedly, you will have to pay a price for such information.