(Fae’re Vinchenstell, “Rise and fall of Northland”, chapter 3rd)
...One of the key for uniting wild tribes of Northland was acquiring support of the grells. These simple creatures driven by killing instinct, almost unable to articulate common speech perceived the Ulrand to be some kind of deity from their primitive beliefs. The reasons for this remains a mystery, though some have speculated that Ulrand was using help of some rogue magician, whose name was lost in the history. (...) After the fall of the Northland, most of grells returned to their conflicted tribes, through pretty sizable numbers have also joined Savage Horde and Meritocracy military rank. As they’re not used to the concept of money, most military officers uses them as primiteve brutes, front-line unit which is perfectly expendable for any planned strategy.
Through grells do poses a bit of similarity to bipeded wolves or worgs, their origins remains a mystery. Most of scholarship believes they’re relicts to the time where the travelling through planes was easier, and they’ve came from different, parallel realm. Through the grells have settled in our world, and became part of it as of now.