Stone-trolls
From Tolkien Gateway
File:Stone Trolls.jpg
Stone Trolls by Angelo Montanini
Stone-trolls were a race of trolls in the service of Sauron. We know nothing for certain of these creatures except that they inhabited the Westlands of Middle-earth. The regions known as the Trollshaws and the Troll-fells (or Ettenmoors) possibly derive their names from this type of troll.
The trolls encountered by Bilbo Baggins and his companions on their journey to Erebor were likely of this kind. If this is the case, the name "Stone-troll" indicates the substance that these creatures transform to when exposed to the light of the Sun. It is unclear whether the Stone-trolls were truly living beings or "counterfeits" crafted by the Dark Lord out of stone.
