Paid All Access subscribers will receive an in-game mail to start the new quests in Zek, the Scourge Wastes.
From: Bailin Grove
Subject: Your Help Is Needed
[Scrawled in some kind of red ink:] Proven friend of the Treefolke, this burl comes to you out of desperation! Grasp it tightly, so that we may speak. Our very survival rests with you!
~Bailin Grove
Right-click a Glowing burl that came attached to the message to summon Bailin Grove the Elder, who gives you the quest.
Notes
You need to be at least level 100 Adventurer to start the Signature Questline.
You must be a paid AllAccess member in order to access this content.
Once you finish Balin's initial quest, other characters on your account will be able to bypass that first quest if you wish, and access thereafter to the zone is via the Ulteran spires.
If you don't get the starting email from Bailin, or you delete it, speak with Jerol <Norrathian Express> in the Village of Shin in Mara.
(100) The Siege of Zek: Rise of The Sanctifiers - (There is only a Solo Quest, after doing that you can do either the Solo Versions or the Heroic Versions of the quests)