“The orcs hindered by the mires that lay before the hills halted
and poured their arrows into the defending ranks. But through them there came striding up, roaring like beasts,
a great company of hill-trolls out of Gorgoroth.”
LOTR: ROTK: B5 C10
Hill-trolls are said to be much like Stone-trolls in many ways, but larger in shape and size and have been described as being covered with greenish hard scales. These Trolls were said to be a man-like in appearance, though it is unknown if they had the capacity of speech. They were fearsome and vicious in battle, bellowing like great beasts, wielding giant hammers with which they beat down their enemies.
Little has been written about these Trolls, for they are mentioned only in passing in the Red Book of Westmarch during the battle of the Black Gate. After the Black Gate opened and the evil creatures of Mordor poured out onto the Dagorlad, it is said that a great company of Trolls surged through the oily mires which stood between the gate and the Captains of the West. They attacked the with a ferocity stoked by the will of Sauron. Pippin the halfling, who witnessed the onslaught described it thusly…
“Then even as he thought these things the first assault crashed into them. The orcs hindered by the mires that lay before the hills halted and poured their arrows into the defending ranks. But through them there came striding up, roaring like beasts, a great company of hill-trolls out of Gorgoroth. Taller and broader than Men they were, and they were clad only in close-fitting mesh of horny scales, or maybe that was their hideous hide; but they bore round bucklers huge and black and wielded heavy hammers in their knotted hands. Reckless they sprang into the pools and waded across, bellowing as they came. Like a storm they broke upon the line of the men of Gondor, and beat upon helm and head, and arm and shield as smiths hewing the hot bending iron. At Pippin’s side Beregond was stunned and overborne, and he fell; and the great troll-chief that smote him down bent over him, reaching out a clutching claw; for these fell creatures would bite the throats of those that they threw down.
Then Pippin stabbed upwards, and the written blade of Westernesse pierced through the hide and went deep into the vitals of the troll, and his black blood came gushing out. He toppled forward and came crashing down like a falling rock, burying those beneath him. Blackness and stench and crushing pain came upon Pippin, and his mind fell away into a great darkness.”
These creatures are also mentioned in the history of Aragorn, whose grandfather Arador was slain by Hill-trolls in the Coldfells, north of Rivendell. It is likely they haunted the Trollshaws, as well as the Ettenmoors and the Highfells in the lands of Rhudaur. As stated above, these trolls were also seen in Mordor in the latter part of the Third Age during the War of the Ring. They may well have been in the ruins of Dol Guldur, though we cannot know for sure, because now none live who remember it.
It is believed that Sauron mixed the blood of the many races of Trolls and Men to create his evil Olog-hai. The Hill-trolls were probably used as breeding stock in this foul-craft, which took place in the dark dungeons of Barad-dûr.
“Trolls are only counterfeits, made by the Enemy in the Great Darkness, in mockery of Ents, as Orcs were of Elves.”