Beasts most often associated with ‘goodness’ are hounds, horses, birds of prey and songbirds.
Huan [‘hoo-ahn] – large wolfhound of Valinor given by Oromë to Celegorm son of Fëanor; understood spoken language but was himself permitted to speak only three times in life; followed his master into exile and was faithful to him until witnessing the imprisonment of Lúthien; assisted her and Beren in their quest for the Silmaril; shortly after killed and was killed by Carcharoth, a wolf of Morgoth.
Eagles of Manwë (Great Eagles) – spirits in eagle-shape (and possibly ‘normal’ eagles as well); messengers and servants of Manwë; lived mainly in the mountains around Gondolin; kept watch on Morgoth and assisted the exiled Elves at times, such as during the escape from the Fall of Gondolin.
~Thorondor- [thor-‘on-dor] Lord of the Eagles of Manwë; ancestor of Gwaihir; often aided both Elves and Men in Middle-earth (assisted in the rescue of Maedhros; rescued the body of Fingolfin after his duel with Morgoth; rescued Beren and Lúthien from Angband).
You know him from: he is named as the ancestor of the Great Eagles of the Third Age.
Nahar [‘nah-hahr] – the great horse of Oromë; white with golden hooves.
Rochallor [raw-‘khal-lore] – the white horse of Fingolfin; bore his master to his fateful combat with Morgoth.
Also around were the Ents: spirits in the shape of trees, or inhabiting trees, summoned by Yavanna; they assisted Beren in destroying the Dwarf army that plundered Thingol’s halls in Doriath, possibly thus starting the long-term grudge between Ents and Dwarves seen in LotR. In LotR, Fangorn (Treebeard) also mentions in a song several lands of Beleriand that he liked to roam.
Beasts most often associated with evil are bats/vampires, wolves/werewolves, spiders, cats, and all dragons.
Ungoliant [oon-‘gol-lee-ahnt] – an evil female being in spider-form; corrupted by Morgoth, but served only herself; ancestor of Shelob and the Giant Spiders of Mirkwood; hungered for light and devoured it; used to hide in the shadowy mountains south of Valinor; after helping Morgoth to destroy the Two Trees she fled with him to Middle-earth; she made her abode in the mountains north of Doriath, spawning there and filling the nearby lands with terror; later departed and nothing is known of her fate; reported to have devoured herself in utmost starvation.
You know her from: – Shelob is said to be “the last child of Ungoliant to trouble the unhappy world”. (TTT)
Dragons – powerful, cunning creatures bred by Morgoth; some -probably all- can speak and enjoy hoarding and guarding treasures; first appeared during the Siege of Angband; played a large role in the Battle of the Sudden Flame and the Fall of Gondolin; most were killed in the War of Wrath. There were both wingless and winged dragons, as well as fire-drakes and cold-drakes. Only four dragons are known by names: Smaug, Glaurung the Golden, Ancalagon the Black and Scatha the Worm.
You know them from: Smaug in the Hobbit; Scatha and Ancalagon named in LotR.
~Glaurung the Golden [glow*-roong (* ‘ow’ as in ‘cow’, not as in ‘low’)] – also called The Father of Dragons; a great, wingless fire-drake; the first dragon to appear; able of speech, foresight and putting people under a spell; appears in the disastrous battles of Sudden Flame and Unnumbered Tears; plays a large role in the tale of Túrin Turambar; led the attack on Nargothrond and resided there after its fall; killed by Túrin.
~Ancalagon the Black [ahn-‘kal-lah-gon] – Morgoth’s mightiest winged dragon; appears in the War of Wrath where he was killed by Eärendil, breaking the peaks above Angband in his fall.
You know him from: Gandalf noted that not even the fire of Ancalagon could destroy the One Ring. (FotR)
Carcharoth (“Red Maw”) [‘kahr-khah-roth] – the mightiest of wolves to ever walk the world; bred by Morgoth himself who put his power on him; guarded the doors of Angband; bit off Beren’s hand along with the Silmaril and fled to the south in madness, killing all in his path, as the Silmaril burnt him from inside; killed and was killed by Huan the hound shortly after.
[b][i]You know him from:[/b][/i] Aragorn mentions him (unnamed) in his story of Beren and Lúthien on Weathertop. (FotR)
Also around perhaps were: the winged beasts on which the Ringwraiths flew as they are reported to be ‘creatures of an older world’ surviving into the Third Age. (RotK)
Orcs – an evil and foul race bred by Morgoth out of captured and tortured Elves soon after their Awakening; they comprise a large part of the armies of Morgoth and Sauron throughout the three Ages; they grow numerous and fierce by the presence of the evil will of their overlords that drives them.
Also called: “orch” (pl. “yrch”); Glamhoth (“din horde”)
Trolls – originally slow-witted, large evil beings in the service of Morgoth; under Sauron’s lead in the later ages they became more clever and dangerous.
Also around was Tom Bombadil, who according to his words has been living in the world since before the first rain and before the Awakening of the Elves.