Half-breed trolls are known for their low intelligence.
After the incident with Cale'anon Vatay, Richard, Krunch Bloodrage, Benn'joon & Sooba which resulted in 126 lost gnome lives, the group came under the employ of Chief Engineer Toyk after he had tried them for murder. The Chief Engineer commanded Fitch to take them to the troll base, and by accident he lead them straight into the front of a marching troll army.
The first troll they encountered was Tim - leading Cale'anon to believe that they were all half-breed trolls due to Tim's stupidity. However, Styx, right next to Tim assured them that they were ordinary trolls, just before capturing the entire group.