Horde players should go to the Orgrim’s Hammer Gunship in the Icecrown Glacier region.  Aboard on the top level to the front-left is a new NPC named Dark Ranger Vorel.  She gives you the quest titled “Inside the Frozen Citadel”.

INSIDE THE FROZEN CITADEL

Dark Ranger Vorel: Come close quickly, I must have a word!

My queen, the Lady Sylvanas Windrunner, has uncovered a hole in the defenses of Icecrown Citadel into a place she referred to as “The Forge of Souls.” She sent word before she left for me to find fierce fighters to send her way.  I think you’ll do.

Go to her within the entrance to the forge.

Quest Objectives: Enter the Forge of Souls from the side of Icecrown Citadel and locate Lady Sylvanas Windrunner.

Alliance players should go to The Skybreaker Gunship in Icecrown Glacier. Find Apprentice Nelphi upstairs in the back of the gunship.  She gives you the same quest.

INSIDE THE FROZEN CITADEL

Apprentice Nelphi: Come close quickly, I must have a word!

My patron, the Lady Jaina Proudmoore, has uncovered a hole in the defenses of Icecrown Citadel into a place she referred to as “The Forge of Souls.” She sent word before she left for me to find any help that I could … and well, I was hoping that might be you.

Please, find her there as soon as you can.

Quest Objectives: Enter the Forge of Souls from the side of Icecrown Citadel and find Lady Jaina Proudmoore.