Here is the God Of War Ragnarök In Plain Sight Favour guide where you need to track down and take out a Soul Eater in The Crater in Vanaheim.
The Soul Eater will count towards one of the Crater Hunts as you work towards Invasive Species and is considered an Epic Hunt on your World Overview.
In order to get to The Crater you will firstly need to complete the Creatures of Prophecy main story quest where you rescue Freyr then, on your back to the Mystic Gateway you will come across Lúnda’s dog, Helka beginning the Scent of Survival Favour, which, once completed, will land you in The Crater.
In order to begin the In Plain Sight Favour you will need to mantle over the cliff in front of you from the Crater Entrance Mystic Gateway (your starting point in The Crater), take a left and swing across the chasm.
Take down the Draugr and Wyvern enemies whilst avoiding the Dragons attacks then head over to the left of the area to find a petrified Ibex you can interact with to begin the In Plain Sight Favour.
Head right from the first Ibex around the next set of rocks to find a petrified Wildebeast you need to interact with.
The third petrified animal carcass which is a Boar is found over to your right against another set of rocks.
Interact with all 3 carcasses then head over to the left to find a new pile of rocks you can throw your Axe at beginning the fight against the Soul Eater.
The fight is simple enough, wait for its chest cavity to open up then throw your Axe or Spear in to the cavity. You can inflict heavy damage if pick up one of the rocks the Soul Eater chucks out and throw it back in to the chest cavity to allow you to get a few critical hits in.
Once the Soul Eater is down the In Plain Sight Favour will complete.