A Rocky End is similar to the previous side-quests you receive from Dave. The only requirement to unlock it, is to finish Final Resting Plains side quest.
Once you do that, head to Cauthess Area outpost where Dave will wait for you in front of a building, across the street from the diner.
Talk to him and he will send you once again to search for a Dog Tag that belongs to a missing hunter.
Objective: Look for the Dog Tag
If you play this quest during the day, you will only encounter level 12 Voretooths, thus you will be able to complete this assignment faster.
The area you have to reach is west from Cauthess Rest outpost, at a crossroads. Drive there, park Regalia nearby, then head to the large billboard and pick up Beautiful Bottle x 1 and Strong Whiskers x 1.
Both of them are on the ground, under the billboard.
Now, move towards the exclamation mark on your mini map. As you approach you will be ambushed by a pack of Voretooths.
A Voretooth from FFXV is a beast weak to ice, shields and lances. Use these weapons to take them out, but constantly move during the fight in order to avoid their fast attacks.
Knowing how to parry is the key here.
Multiple Voretooth Bristles are looted from these creatures.
Objective: Retrieve the Dog Tag
After the area is cleared, look around for a large rock. If you go around it you can find several Debased Coins.
The Dog Tag for A Rocky End side-quest is also located near the said rock as you can see in the picture above.
If you have difficulties finding this item, open your map and search the south-western part of the blue circle.
Just go around the rock and look for a yellow sparkling object on the ground. Pick it up to update your objective.
Objective: Deliver the Dog Tag to Dave
All you have to do now is to drive back to Dave and give him the Dog Tag you collected. In exchange, you will receive the rewards listed below.
Once A Rocky End is completed, Dave relocates to Taelpar Rest Area outpost, which is located south-west from your current location. Here you will be able to play the next quest in line, named Swallowed by Shadows.
Since the enemies you encounter during Swallowed by Shadows are level 20, we recommend you to postpone this quest and follow our directions below.
A Rocky End Quest Info
Description: “Yet another hunter has fallen, and Dave needs help retrieving their dog tag. Noctis agrees to venture into the wilderness and find the tag for the sake of the bereaved family.”
Reward: Hi-Elixir x 10
Post Quest Suggestion
Complete The Trial of Titan main-quest.