The Frost wold is the weaker and domesticated version of the Winter Wolf. As the elves arrived in the north and joined the local human settlements, they were in search of a faster way to travel in the heavy snow and the slippery ice. Some Winter Wolves were interested in joining with the settlement (in return for the elves and human food, and luxury. After a long period of time of joining the northerners, they become the Frost wolf we know.   The winter wolves are very loyal and loving to their master, and it usually goes both ways.