Cave-trolls

Cave-trolls are a race of trolls found within the caverns of the Misty Mountains. Cave-trolls were discovered from an encounter with the Fellowship of the Ring as they passed through Moria, but were evidently found elsewhere in Middle-earth, too. These trolls, along with Orcs and perhaps other creatures, were originally sent to inhabit Moria by Sauron about five hundred years before the War of the Ring.

Appearance and First Discovery by humans.
Cave-trolls' heights can range from 11 to 19 feet. They retain dark-yellow skin with tinted blue hues and purple eyes. Their blood is black in color, and very hot. Their hides cannot be pierced by normal swords, and remain hard to pierce even when confronted by Elven blades.

Habits
Cave-trolls are intelligent creatures, though most travellers and adenturers often underestimate the intillegence of the animal. They use their sense of smell more often than sight, generally being brought into combat by a chain around it's neck, led along by a goblin tamer. In combat Cave-trolls usually kill the opponents that foolishly get too close to them. Even if they are allied with them. Cave-trolls are one of the shortest types of troll unlike Mordor trolls, though they are shown only in The Lord of the Rings: The Battle for Middle-earth II: The Rise of the Witch-king. Cave Trolls are probably the second stockiest, behind the Olog-Hai.

Cave-trolls are omnivores, eating both meat and plants. Usually these trolls live with groups of goblins and fight alongside them or in groups of two or three in small caves. They are made and used by the armies of the Sauron (Though Sauron would fore go these trolls in favor of Olog-Hai, a stronger, smarter and larger troll that could move in the sunlight without turning into stone). It is known that Cave-trolls can turn into stone when exposed to direct sunlight. The Cave Trolls have a very primitive form of language. As depicted in The Hobbit. They can speak Westron (Common speech) but it is not proper in any way. Cave-trolls wear loincloths which the trolls either find or are given by the Goblins. Some Trolls in the wild make them from dead animal hides.

Location
Cave-trolls dwell in such places as the hills on the feet of the Misty Mountains or in its caves. The Elves prevent the cave-trolls from getting far in the south so they thrive in places such as the badlands of Ettenmoors or the Troll Fens. These brutish creatures are then captured by the goblins to be used in their armies.

Book and Movies
In the book version of The Fellowship of the Ring there are many cave-trolls. The first cave-troll is fought by Frodo who stabbed its foot, but the troll is not killed. The trolls are described as having long arms, dark green scales and toe-less feet. Soon, two more cave trolls throw two large boulders to form a bridge so the Balrog could pass.

In the Peter Jackson's 2001 movie version, there is one cave-troll which is killed by the Fellowship members who spear and hack at the cave-troll with no avail until Legolas dispatches it with an arrow. The arrow enters the soft part of its mouth and goes straight through the troll's neck, emerging from the back of its head after becoming stuck in the troll's thick skull. In the movie made by Peter Jackson the cave troll is computer animated. Its movements were done by Randall William Cook, wearing a motion-capture suit. It also has a set of nostrols located higher than the space between its eyes, making its nose look almost like a "third eye".

In Ralph Bakshi's animated movie, the cave-troll has quite an inconsequential part. Gandalf says "Orcs and something else! A great cave-troll I think!" when he sees the orcs through the east gate. Boromir then closes the gates but they are barged open by a large creature covered all in fur apart from it's hands and feet (Presumably the cave-troll). After this, Frodo leaps towards the creature, stabbing it through the foot, shouting "For the Shire!" as he does so, causing it to flee.

Battle For Middle-Earth
In the EA game, Lord of the Rings:Battle for Middle-Earth, cave trolls are spawned from a cave. They are neutral and attack any units in the area. When your soldiers destroy the cave, a pile of gold can be found suggesting that trolls like to collect trinkets.This is supported in The Hobbit .After the trolls are turned to stone, Bilbo finds a large stash of treasure in their cave. Strangely, cave trolls in the afore-mentioned game are a brownishh color instead of the Greyish-Green seen and described in the movie and book.

In The Battle of Middle-Earth II they revert to their original greyish-green that was seen in the movies and books. The goblins can train them out of a fissure as a lesser siege unit, inferior to the mountain giant. The troll can throw rocks or fight with their fists. when using melee they can find an orc/goblin and throw it on an enemy. They can also fell a tree and use it as a giant club, this greatly improves their damage and it makes it possible to bash entire battalions. Disavantages of this are that when the troll picks up a tree, he will keep it untill his death. So he can't throw rocks anymore or throw goblins/orcs as ammo. All of this also works with the mountain trolls that mordor uses. The only diffrence is that they look different, and the mountain trolls can eat the orcs for health instead of throwing them.

Cave trolls in Lord of the Rings: Conquest
There is also a cave troll in Lord of the Rings: Conquest made by EA Video Game Co. But these are seen only briefly and also they are based upon the Mordor troll catapult loaders at Pelannor fields, wearing strange leather helmets. Thus conflicting the movie. The Cave trolls are playable in Lord Of The Rings:Conquest but the trolls spawn randomly by type so it is hard to play as a cave troll in Lord Of The Rings:Conquest. they are weak to head shots and grabs like other trolls but take more damage