LOTR: Bag End Inn

Large creatures of great strength frequently in the service of the Enemy. Trolls were humanoid in shape but monstrous in appearance. They were much taller and broader than Men. They had scaly skin and large flat feet with no toes, and their blood was black.

Trolls were generally rather stupid. They did not build or create anything. Trolls hoarded riches that they stole, and they often ate the people they robbed. Trolls had no language of their own, though some Stone-trolls in Eriador were able to speak the Common Speech and Sauron taught Trolls in his service the Black Speech.

Trolls were incredibly strong and powerful and difficult to kill. Their main weakness was that most Trolls turned to stone when exposed to sunlight.

Trolls dwelled in Mordor, southern Mirkwood, the Misty Mountains including Moria, and in the Ettenmoors in Eriador, where the woods called the Trollshaws were located.

Trolls lived in a variety of habitats. There were Cave-trolls, Hill-trolls, and Mountain-trolls. There may even have been Snow-trolls: Helm Hammerhand was compared to one, though no other record of such a creature exists. Stone-trolls may have been a specific breed of Troll, or this may have been a general term that applied to all Trolls that turned to stone in sunlight.

Trolls may in fact have been made from stone originally. It is said that Trolls were made by Morgoth, possibly in mockery of the Ents. Tolkien was uncertain of their origin:

"I am not sure about Trolls. I think they are mere 'counterfeits', and hence ... they return to mere stone images when not in the dark. But there are other sorts of Trolls beside these rather ridiculous, if brutal, Stone-trolls, for which other origins are suggested."

By "other sorts of Trolls," Tolkien apparently meant the Olog-hai, a superior breed of Troll created by Sauron at the end of the Third Age. It is not known what method or stock Sauron used to breed this new kind of Troll. In an unpublished note, in what appears to be a reference to the Olog-hai, Tolkien suggested that "It would seem evident that they were corruptions of primitive human types." (HoME X, p. 414)

The Olog-hai could withstand direct sunlight and they were more cunning than other Trolls. They were large and powerful and their skins were as hard as stone. They understood the Black Speech, though they rarely spoke. They lived near Sauron's stronghold of Dol Guldur in southern Mirkwood and in the mountains of Mordor. The Olog-hai were entirely under Sauron's command and acted solely in his service.

As Sauron's power grew, Trolls became more of a menace in Middle-earth. Aragorn's grandfather Arador was killed by Hill-trolls in the Ettenmoors in 2930.

On his adventure in 2941, Bilbo Baggins met three Trolls named Tom, Bert, and William Huggins. These Stone-trolls roamed the Trollshaws and they had a cave there where they kept the riches they acquired, including Glamdring, Orcrist, and Sting. It is not known where or from whom the Trolls obtained these swords.

Tom, Bert, and William spoke the Common Speech, though rather poorly. They ate mutton and passing travellers when they could get them. They were pleased to capture Bilbo and the thirteen Dwarves, but Gandalf tricked them into arguing over how to cook them until the sun rose and the three Trolls turned to stone. They remained there like statues; Frodo Baggins and his companions saw them 77 years later while travelling to Rivendell.

The Fellowship encountered live Trolls several times during their quest as well. In Moria, they were attacked by a Cave-troll, which Frodo stabbed in the foot.

Mountain-trolls wielded the great battering ram Grond at the Battle of the Pelennor Fields and destroyed the gates of Minas Tirith.

A great company of Hill-trolls from Gorgoroth fought at the Battle of the Morannon. Since the battle took place during the day, these Hill-trolls may have been of the Olog-hai strain. The Hill-trolls struck down many Men of Gondor with their heavy hammers. The Troll-chief wounded Beregond and would have bitten his throat, but Pippin Took stabbed the Troll with his sword of Westernesse, which he later called "Troll's bane." After the battle, Gimli found Pippin alive under the Troll's heavy carcass.

After Sauron's downfall, the Trolls in his service became mindless and directionless without his evil will to guide them. Some slew themselves and others fled and hid. At the beginning of the Fourth Age, the Men of Gondor and Rohan continued to hunt down Sauron's servants, and it is likely that in time Trolls ceased to pose a threat to the peoples of Middle-earth.

The ending hai in "Olog-hai" may be a collective plural denoting "race, people" derived from the Sindarin li meaning "many." Alternatively, it may be derived from the Sindarin gae meaning "dread."