With the information you gleaned from the hunters of Tailfeather, Alphinaud is eager to check with the Vath.
This quest is available if you have completed the quest In the Eye of the Beholder.
Starting the Quest
Talk to Alphinaud in the Dravanian Forelands to begin the quest.
Speak with the Vath Storyteller
Go southwest to where the orange arrow is pointing in the minimap. Talk to the Vath Storyteller and there will be a cutscene.
Proceed to Loth ast Gnath
Go south to where the orange arrow is pointing in the minimap. Enter the purple circle and defeat the Gnath Firedrone and Gnath Steeldrone.
Wait for Your Comrades
Go east to the quest icon on the map and check on the sparkling Destination to proceed. There will be a cutscene. This one is important, so it is recommended to watch it either now or via the Unending Journey in an inn room. (Main Scenario 1 > Dragonsong Main Scenario Quests > A Little Slow, a Little Late > Cutscenes 1, 2, 3, and 4.) After you watch it, you may find it interesting to watch the original trailer for A Realm Reborn, which was released two years prior to patch 3.1, which included this quest.
Speak with Thancred
Talk to Thancred to complete the quest. There will be a cutscene.
Next Main Scenario Quest
After you complete the quest, talk to Alphinaud to accept the next quest: Dreams of the Lost. There will be a cutscene.