For access to the Tree Portal in Candeth Keep, speak to the three NPCs in a tent in Wai Jhou. Then give the three of them a total of 100 partial bags of salvage (each one takes a different type of salvage). That is 100 bags total, to in any combination to the three NPCs. For example you could give 50 to one, 25 to another and 25 to the last one.
Once you've handed 100, you are flagged to use the portal and will be given a Candeth Keep Stamp. You can continue giving bags if you wish, once you hand 100 to each NPC individually you'll get a hat reward (different hat from each NPC).
Caelis Renning tells you, "Hail friend, my name is Caelis. The Aluvian, Sho, and Gharun'dim peoples united under Queen Elyssa have joined together to form the Isparian third of the new alliance."
Caelis Renning tells you, "We are assigned to this outpost near Wai Jhou, to collect building materials for the continued upkeep of Candeth Keep. I will accept all types of salvaged metal and wood that you can afford to donate to the cause. Large or small, poor or priceless, your donations will be treated equally."