The Ghost of Uther Lightbringer shows up briefly during a quests offered by a Blood Elf located at the Bulwark in Tirisfal Glades. You are sent by the Blood Elf to defile Uther’s Tomb but it fails. The Ghost of Uther Lightbringer sends you back to the Blood Elf to deliver a message … he forgives his old student. Read more
Thanks, Deathkore for the heads up.