If he wants to achieve complicated things through the puppy, he will have to take control of it directly with his mind. Until then, the puppy will continue to act based on its instincts.
For now, he let the puppy run wild on its own. It can be considered a form of indulging himself.
However, Fenrir's antics soon became pitiful to see because all of that sand that it ate could only bring it to a tenth of the way from rank 1 to rank 5. Loki couldn't take it anymore, so he granted Fenrir more of his power.
As soon as he granted Fenrir the authority to use the Power of his Mental World, all of the black teeth in the puppy's mouth became multicolored. This immediately delighted Fenrir.
Now that it had more power at its disposal, the puppy turned away from the wall of sand and went back to the corpse on the ground. It stopped some distance from the corpse and activated the borrowed power.
