Long ago the Tla'mxi lived in the eastern mountains, far from their current home in the northern forests of Salnar. Then came the Trolls. The tales they tell of their origins are varied, but the most common holds that a group on the Wolf-Running found a mage attempting to maintain control over a summoned creature (whether it was an elemental, or some strange denizen of another plane is unclear). Whatever it was, he was proving unable to master it. Rather than make an attempt to dispel the being, the mage drained the intelligence, as well as much of the life from the band and their companions [Note: Companions here means wolves, and is being used in a very Valdemaran sense.] . When he focused this new power upon the creature, it melded with it, creating the first Troll. After killing the wizard, it infused a small amount of itself into the Wolf-Runners, who were, in effect, the perfect templates. Each of these became a weaker, but still dangerous beast, similar in form to the original.
[I'll post a statblock here if/when I get around to it]