Toss a Seed to Your Hunter...

Related to the [npc=171690] rare in the Ardenweald Shrouded Mire zone.
You can find [object=364345] in the Ardenweald on the ground.
It's just zone-wide grass object you can find all over the area.
[item=183902] is inside and when you start the fight you will see extra action button to toss it

You will see [npc=174365] and [npc=171690] (The Winter Wolf) Talk to the [npc=174365] to start the fight
And the fight itself isn't hard because [npc=174364] will assist you and tank the [npc=167724]

/way 65.74 22.91 Rotbriar Changeling (The Winter Wolf)

Faintly Glowing Seed spawn location: https://youtu.be/dWZ2g8m9tWY
Toss a Seed to Your Hunter... achievement https://youtu.be/_oVGyFP8Y6s

Toss a Seed to Your Hunter... achievement and the rare is a reference to the The Witcher
https://en.wikipedia.org/wiki/Toss_a_Coin_to_Your_Witcher

If you are carrying a Faintly Glowing Seed in your bags, then you will get an extra action button during the fight with [npc=171690]. Use it and you instantly get this achievement!

This achievement is hidden until earned. Makes me wonder if there are others like that