The Tome of Divinity
Take the Symbol of Life to Gazin Tenorm in Stormwind.
Take this, <name>. It is called the Symbol of Life.
You've proven charitable and patient, and now the time has come to see if you're powerful enough to focus one of the Light's greatest gifts.
My friend Gazin returned recently from an encounter with some Defias in Elwynn near Heroes' Vigil--he barely escaped with his life. He's near the altar having his wounds healed by our priests.
Take the Symbol and speak to him. If you can help him, then we will speak again soon. May you bask in the Light's glory.
Pleasure to meet you, <race>. Don't mind my wounds, the good priest here can take care of ol' Gazin this time. I won't be needing the power of that Symbol of Life you've got there... not yet anyway.
So, Duthorian sent you to speak to me, huh? Fair enough. I'll tell you exactly what befell me and my friend Henze. And with any luck, and some skill on your part, perhaps you can still help us all.
The entirety of this quest happens at Stormwind City