The Olog-hai are not mentioned by name in The Lord of the Rings; the term appears only in the appendices. They were bred by Sauron in the late Third Age, possibly for the same reason Saruman bred the Uruk-hai, for improvement and less vulnerability to sunlight. They lived primarily in Mordor and in southern Mirkwood. However, they are described as being in the Battle of the Black Gate, where Pippin saves his friend Beregond from one.
The Olog-hai are described as being taller than a Man, covered in spiky scales, carrying war hammers, large swords, or spiked maces, and bucklers, and having claws and, on occasion, tusks. It is mentioned that after the War of the Ring, all Olog-hai were killed.
Olog-hai was a Black Speech word that meant simply 'troll-folk'. They seldom spoke and never in any language other than the Black Tongue of Mordor. 'Olog' meant 'troll' in Black speech and 'hai' meant 'folk’. 
Olog-hai lacked typical troll vulnerabilities: they were very intelligent and able to move under the Sun, unlike their counterparts. For this reason they were seen by some to be Orcs like the Uruk-hai, but of troll-stock.
Portrayal in adaptions Edit
The Lord of the Rings film trilogy Edit
- "You are soldiers of Gondor! Whatever comes through that gate, you will stand your ground!"
- —Gandalf, The White Rider, shortly before several Olog-hai blast through the main gate of Minas Tirith
Olog-hai were depicted as large trolls in the motion picture The Lord of the Rings: The Return of the King, clad in dark armor and wielding the war hammers alluded to in the appendices. In the Siege of Gondor they were primarily used as shock troops after the gates of Minas Tirith were broken, although later an Olog-hai duels Aragorn at the Black Gate and nearly kills him.
They differ from the other trolls depicted in the movies in that they have more forward-facing eyes as well as hair on their bodies. They are usually grey, dark green, reddish-brown, or black in color. They have twenty-four teeth and have an average height of about ten to fifteen feet, compared to regular Trolls who were eight to ten feet.
Their eyes are also bright orange, showing their evil connection with Sauron. Attack Olog-hai wear breastplates, vambraces, pauldrons, and helmets, and carry maces, hammers, or huge swords. Despite their size they were exceptionally fast and were skilled enough to parry and engage in swordplay, as was the case with one that duelled Aragorn outside the Black Gate.
The Hobbit Films Edit
In the Hobbit film adaptations, more specifically in The Hobbit: The Battle of the Five Armies, Sauron's chief orc lieutenant Azog commands a few dozen armored Olog-Hai of Dol Guldur along with thousands of war-bred Moria Orcs. In this film the Ologs appear much like they did in the Lord of the Rings trilogy, however there are some key differences.
Most of the trolls are much larger than any other variety seen thus far. (standing about 25 - 30 feet tall) rather than the standard 10-15 feet height for most other Ologs. The trolls are mostly dark grey and tan in color. Some have large tusks protruding from their lower jaws. Unlike their Mordor cousins they wear armor similar to that of the orcs living in Moria.
Shadow of War Edit
The Olog-hai that appear in this (non-canon) game have certain similarities to the trolls that appear in both the Hobbit and Lord of the Rings film adaptations. There are certain differences though. Some of these Lesser Ologs that appear are smaller in size than those that appear in either film adaptation and stand about in between 9 to 11 feet in height. Interestingly enough even though they do speak the black speech on occasion, they mostly speak the common speech (Westron/English) even though Olog-hai are supposed to only be able to speak the black speech, and very sparingly at that.
The possibility as to why the Ologs are so small and resemble the in-game Uruks so much is most likely the fact that the developers didn't want anything comparable to their currently existing in-game "troll variant" beast, the Graug. Strangely enough the Graugs that appear resemble true Olog-Hai in size and mindset more so than the actual Olog-hai that appear in the game.
Non-Canonical Olog-hai Edit
|Foreign Language||Translated name|
|Kazakh||Олог-һаі (Cyrillic) Olog-hai (Latin)|
|Kyrgyz Cyrillic||Олог-йаи ?|
|Serbian||Олог-хаи (Cyrillic) Olog-hai (Latin)|
|Uzbek||Олог-ҳаи (Cyrillic) Olog-hai (Latin)|