Earlier today on Mangler I killed 3 a dire wolf pup in Icefall. They were inside of the northeast castle. They conned light blue and did not con as a rare creature.
Later today I went back to Icefall and saw dark blue a dire wolf pup along with Grimjaw near the other dire wolfs that are close to Valdeholm zoneline.
These pups with Grimjaw conned as rare creatures and were in fact the right ones for the Hunter of Icefall Glacier achievement.
No idea how to spawn Grimjaw or anything though.
Good luck!