After finding the Dead Acolyte go back to the inn in Goldshire, seek help from the warlocks in town. After that you will receive an item to use on the Dead Acolyte and will have to deliver the note to the warlock in Stormwind Gakin the Darkbringer. He is on the warlock training place in Stormwind. It’s easier if the Heartstone is set to Stormwind. After talking with Gakin the Darkbringer he will give you the Warlock rune Demonic Tactics.