Many great powerful priests have earned the title 'Heirophant' in the past, for their ability to conjure and imbue the Light within great enchantments. This skill is extremely difficult, and only passed on from one master to a student of great standing. Over time, the number of Heirophants have fallen and with it, the invocations of our past have faded to obscurity, lost to the pages of history.
For your selflessness I can offer you such an invocation, but I require a rare material. My powers have wained, and I require a single Overcharged Ley Energy. This energy can be found within the tower of Karazhan. Bring me one, and I can offer you the invocation of your choice.