Swalled By Shadows - Taelpar Rest Area
First Available: Chapter 3
Other Requirements: Complete A Rocky End
Location: Taelpar Rest Area
Rewards: 1,200 EXP & 10 Hi-Elixirs
To begin this quest you'll first need to complete A Rocky End from Dave, after which he'll be found at the Taelpar Rest Area. After you accept this quest but before leaving town be sure to speak to the owner of the Diner, he'll place a more exact mark on your map for this quest (along with place many other useful markers on there for you if it is your first time talking to him).
For the Swallowed by Shadows quest you'll have to go to the southeastern portion of Duscae, in the same area as the Of Gods and Kings quest from Vyv. You'll find the Dog Tag that you need for this quest at the lumbermill in the middle of the quest marker.