WoW quest question 'Bring the light'?

I'm a level 43 night elf rogue. There's this quest given by Archbishop Benedicus in the Cathedral of Light, Stormwind which requires you to kill Amnennar the Coldbringer a dungeon boss in Razorfen Downs. I went to the cathedral but the bishop wasn't giving any quests. So I thought that maybe the quest was given in the dungeon but there's no mention of it there either. After I killed the dungeon boss, I went back to the Cathedral but there's still nothing and the only thing the archbishop will say to me is 'welcome to the cathedral of light.' The quest's 'Bring the light' by the way. Any requirements for the quest I don't know of? Or any solution to my predicament? Thx :)