Helarjar Landing: Vrekt

I found that the easiest way is to take the Flight Path to Hafr Fjall.
Then ride down the side of the cliff to the area with the PvP Watch Tower (sometimes a PvP World Quest area).

Just shortly before you reach the Watch Tower, head East and continue down to the water. From here, it's a quick and straight run/swim to the quest area which lies just at the beach as the map indicates.

It of course helps to have water walking or a Water Strider.

My apologies but I'm not sure why some people are suggesting to skip this quest.

While you doing this World Quest, Helajar mobs like [npc=116601], [npc=116600] and [npc=116180] will drop [item=142487] needed for the Trial of Valor Quest Trial of Valor: The Lost Army, which is obtained from [npc=114263] after you kill it and complete Trial of Valor: Odyn's Favor.
After I killed the 10 needed for the World Quest they stop to drop fragments.

Video Guide: https://youtu.be/LQUEaC72V4c

Currently, this quest is visible on the World of Warcraft Legion app, but is not visible from the map in the game itself. Regardless, if you approach the area, the world quest will trigger.

This world quest will become available once you complete Helya's Conquest. In the small town of Vrekt, which can be reached either from following the coastline southeast of Greywatch, or from the water to the west or south (it's never very convenient to reach), you will find this world quest. You will need to kill any 14 vrykul/helhound enemies in the area. The Vrykul enemies that count for this world quest include [npc=116600]s, [npc=116601]s, and [npc=116180]s. [npc=115846], who also must be killed, a skeletal vrykul that can be found on the upper tier of the village. You will find him in the northeastern corner of the upper tier of Vrekt chaining down a neutral [npc=107830]. Once you kill these enemies, the world quest will be complete.