Little is known for certain of the beginnings of the Orcs, the footsoldiers of the Enemy. It is said that they were in origin corrupted Elves captured by Melkor before the beginning of the First Age.
In appearance, Orcs were squat, swarthy creatures. Most of them preferred the darkness, being blinded by the light of the Sun, but the kinds bred later in the Third Age such as the Uruk-hai could endure the daylight.
GREAT ORCS: The fighting Uruk-hai.
A common name for the large soldier-orcs of Mordor and later also Isengard that troubled Gondor and Rohan in the late Third Age. In fact, this name is only ever used by Éomer, and may only have been current in Rohan, but the fearsome creatures it described had been known for five hundred years when he spoke these words: creatures whose name in their own Black Speech was Uruk-hai.
DRAGONS: The Worms of Morgoth.
Mighty reptilian creatures who ranked among the most feared of the servants of the Dark Lord. Of the origins of dragons, no tale tells; the first of them to be seen was Glaurung, Father of Dragons, who first issued from Angband in the middle of the First Age. After Glaurung came many others to strike fear into Elves and Men for the next three ages; among them were Ancalagon the first winged dragon, Scatha who dwelt in the cold northern wastes, and Smaug, last of the great dragons.
Dragons have powers of intelligence and speech, and many are also able to cast the dragon-spell, a bewildering confusion that effects any who gaze into the eye of the creature.
The dragons were not destroyed at the end of the Third Age; some are said to have survived to our own time, but the great worms and drakes of the Elder Days are no more.
BALROGS: Dread Servants of Melkor.
The Balrogs were spirits of fire seduced by Melkor in the beginning of Arda, and who dwelt in his northern fortress of Utumno. During the First Age, the Balrogs were the most feared of Morgoth's forces after the dragons.
In appearance, the Balrogs were man-like, but fire streamed from them, and they were swathed in dark shadows. They carried whips of flame and induced great terror in friends and foes alike.
In the War of Wrath, Morgoth was assailed by the forces of the Valar. Most of the Balrogs were destroyed in that War, but some few escaped over the Blue Mountains and lay hid in Middle-earth. Durin's Bane, the creature that drove the Dwarves from Moria, was one of these.
The Balrogs Before the First Age
The Balrogs were in origin Maiar, of the same order as Sauron or Gandalf. Melkor corrupted them to his service in the distant past of the World, in the days of his splendour. They were originally gathered by him in his ancient fastness of Utumno during the time of the Lamps of the Valar. When this fortress was destroyed by the Valar, at least some fled and lurked in the pits of Angband (whether any of the original Balrogs were slain in the Valar's attack on Utumno is not known).
Balrogs in the First Age
When Melkor and Ungoliant escaped from Valinor three ages later with the Silmarils, the Balrogs were still to be found in the ruins of Angband. Ungoliant entrapped Melkor in her webs, demanding the Silmarils for herself, but the Balrogs issued from their hiding-place and rescued their lord.
The Balrogs were apparently first encountered by the Elves during the Dagor-nuin-Giliath in the first year of the First Age. After the great victory of the Noldor over Morgoth's Orcs, Fëanor pressed on towards Angband, but the Balrogs came against him. He was mortally wounded by Gothmog, Lord of Balrogs. Though his Sons beat off the demons of fire, Fëanor died of his wounds soon after, and his spirit departed for the Halls of Mandos.
The Appearance and Nature of Balrogs
Balrogs were spirits of fire - their hearts were of fire, we are told, and they carried whips of flame. They could, however, shroud themselves in darkness and shadow. The Balrog that Gandalf fought in Moria, for example, at first gave no hint of his fiery nature apart from the flames that issued from his nostrils.
TROLLS: Hulking Monsters of the Dark.
CAVE TROLLS: Trolls apparently adapted for underground life. The Company of the Ring discovered them when they passed through Moria.
HILL TROLLS: A variety of troll adapted for life among hills and moorland. Aragorn's grandfather Arador was slain by them in the hills north of Rivendell, and a company of these creatures were among the armies that Sauron loosed from the Morannon in the last battle of the War of the Ring.
MOUNTAIN TROLLS: Trolls from the highland regions of Middle-earth. It was creatures of this kind that weilded the great battering-ram, Grond, at the Battle of the Pelennor.
OLOG-HAI: A strong race of Trolls bred by Sauron at the end of the Third Age. Unlike others of Troll-kind, they could endure the light of the Sun.
SNOW TROLLS. Trolls that lived among the ice and snow. No snow-troll appears in Tolkien's work, but we can infer their existence from the fact that Helm Hammerhand is compared to one of these creatures during his sorties against the Dunlendings during the Long Winter.
STONE TROLLS: Lumbering creatures of the night. 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 trolls encountered by Bilbo Baggins and his companions on their journey to Erebor were likely of this kind.
GOBLINS: The race of Orcs.
A name for Orcs, and especially the smaller kinds that infested the Misty and the Grey Mountains in the later Third Age, and had their capital at Mount Gundabad.
OGRES: A mysterious and fearsome race.
Monstrous and destructive creatures of legend and folklore. In fact, it is doubtful whether Ogres ever existed in Middle-earth. Tolkien mentions them only once, in The Hobbit, during Bilbo's Riddle-game with Gollum. In his attempt to solve Gollum's fifth riddle, Bilbo '...sat in the dark thinking of all the horrible names of all the giants and ogres he had ever heard told of in tales...' Since no ogre is ever again mentioned, it is entirely possible that they were a mythical race even to the inhabitants of Middle-earth.
BATS: Fluttering creatures of the night.
Flying creatures of the night, traditionally associated with the forces of Morgoth and of Sauron. They were most famous in Middle-earth for taking the part of the Goblins during the Battle of Five Armies.
VAMPIRES: Bat-winged creatures of darkness.
Mysterious bat-like creatures in the service of Morgoth and of Sauron. The only vampire that Tolkien names is Sauron's servant Thuringwethil, but Sauron himself took the form of a vampire on at least one occasion.
WEREWOLVES: Enchanted servants of the Dark Lord.
Dread servants of Morgoth in wolf-form. Werewolves were especially associated with Sauron, who indeed took the shape of a great wolf himself at least once.
BARROW-WIGHTS: Evil spirits out of Angmar.
Evil spirits sent to dwell in the Barrow-downs by the Witch-king of Angmar during his wars with the remnant of Arnor, and who remained there long after the realm of Angmar itself had vanished from the world.
SERPENTS: Writhing creatures of the Dark Lord.
Creatures of Morgoth. Sauron took the form of one during his battle with Huan.
SPIDERS: Eight-legged spinners of webs.
Though they were common throughout Middle-earth, the most fearsome of all spiders were Ungoliant and her descendants, including the giant, intelligent variety found among the dark trees of Mirkwood.
WARGS: Monstrous wolves of the northern lands.
The ferocious and intelligent race of wolves that lived in the northern Vales of Anduin, and probably elsewhere in the north of Middle-earth.
