(Yes we just now finished it.)
After you defeat Lord Valthalak you have to "use" his amulet on the body and it spawns this talkable spirit, who completes that step of the quest. Image was taken with UI still turned on for proof of who was there to defeat him, as thanks.
This is as proof that it's me and that it is the full set.
I stopped by Thunder Bluff after completing the quest, and thanked the Archdruid for setting me down the path of Nature.
Pausing to reflect on adventures past as I look over my homeland.
I am now the proud owner of a full set of Feralheart Raiment.