"Wenn das Böse nicht mehr geballt auftritt, sondern sich dünn über die Welt verteilt, befinden wir uns jenseits vom
Schwarz und Weiß der Mythologie." - William Carter

A clash between good and evil?

During the history of Middle-Earth several wars allied its good peoples against the evil power of Melkor or later his mightiest servant Sauron, which rouses the impression of a population devided into good and evil according to the traditional mythologic scheme of Black and White. But can such a complex structure as Tolkien's Middle-Earth really be described as easily as that? A closer look at its tribes and races will tell.

The evil power of Mordor: Sauron, his orcs and the Nazgûl

"Deep in his castle he said:
'All land will be mine,
there's one thing for sure:
The triumph of shadow is near!'"
Blind Guardian - "A Dark Passage"

Originally, Sauron was a Maia of the Vala Aulë, but followed the traitor Melkor (later called Morgoth, the Dark Enemy, and not counted as one of the Valar anymore) who had been the highest of the Valar, but had been estranged from them by his desire to command over others (quite compairable to the fallen biblical angle Lucifer) and in his jealousy of the work of the other Valar had tried to ruin everything they had made during the Shaping of Middle-Earth. After Morgoth had been defeated by the Valar and the Calaquendi in the War Of Wrath, Sauron succeeded him in his evil work. At first he fled the Elves and lived in hiding until the Valar, whose punishment he feared, had withdrawn across the sea to Valinor, but then he built Barad-Dûr, the Dark Tower of Mordor, and betrayed the Elven-smiths in Eregion
by seducing them to forge the Rings of Power and then forging the Ruling Ring that would force the bearers of the lesser Rings to obey his will. He was assailed and taken prisoner by the Númenórians, but he gained influence over them and achieved the fall of Númenór. Having lost his body in the destruction of the island, his immortal spirit returned to Mordor where he was defeated by the Last Alliance of Elves and Men and Isildur cut the One Ring from his finger. Isildur, however, held back by the Ring's power, dinot destroy it and so Sauron - weakened, but not wiped out - could continue his reign of terror from the fortress of Dol Guldur in Mirkwood. There he was able to increase his power until he was strong enough to return to Mordor where he bred a vast army of orcs for the War of the Ring in which the whole of Middle-Earth should be defeated and fall under his reign. But before he could reach his aim, the Ring - and with it Sauron's power - was destroyed by the hobbit Frodo Baggins.

The orcs

"Screaming and shouting, yearning for blood
Sevants of Melkor the evil god
Riding with wolves, runners of night
Hordes of the Eye, the black blades of might"
Battlelore – Attack Of The Orcs

Sauron's servants, the orcs, were alienated Elves created by Morgoth, hating everything except for annihilation and murder, including their master and their own kind, and especially hating and fleeing the sun and the Elves. They were small ugly creatures with black skin, yellow fangs and small red eyes, armed with daggers and short swords; cold black blood ran through their veins and their build resembled that of apes. Their language, an estranged mixture of various human and elvish languages, barely allowed them to communicate with each other and usually served the purpose of cursing. All they thought about was war and fighting and they were content as long as they were allowed to desolate, torture and kill, but they were very cowardish and attack only if they were in the majority.
When they had the chance to run away from their master or in the times when he was in hiding, they lived in cave systems under the mountains where they often gathered around mighty evil creatures such as cave trolls or the Balrog of Moria.

The Nazgûl

"Nine silent horsemen
Riding forever for their lord
In the night which shall never end."
Battlelore - The Curse Of The Kings

A special role in the hirachy of Sauron's servants was taken by the Nazgûl, the Ringwraiths. Once having been nine powerful kings and sorcerers, they had been given the Nine Rings by Sauron, and, blinded by their greed, had not realized that the power of the the Ruling Ring was slowly turning them into wraiths, invisible to mortals, neither dead nor alive and always following Sauron's will. They were blind, but they could sense the power of the One whenever it is near them and - taking the shape of black Riders - they hunted whoever bore it, ever longing to bring it back to their master. Their screams filled the hearts of their enemies with terror wherever they showed up and the slightest scratch of their poisonous blades was enough to turn their victim into one of them unless it was healed by the skill of the only beings they feared - the Elves whose sheer touch could lesson the pain of such wounds. (10)

The power of the Ring

"There are signs on the Ring
Which make me feel so down:
There’s One to enslave all Rings,
To find them all in time
And drive them into datkness,
Forever they’ll be bound"
Blind Guardian - Lord Of The Rings

There is also a small group of what you could call "involuntary renegades" taking up a special status among the evil beings of Middle-Earth:
In the Second Age, Sauron persuaded the Elven Smiths of Eregion to forge the Rings of Power, Three for the Elven Kings, Seven for the Dwarf Lords and Nine for Mortal Men. Then he made the Ruling Ring that had power over all the other Rings so he could command the will of their bearers. In this Ring he included some of his own power, so that when Isildur cut the One from his finger in the Battle of the Gladden Fields, Sauron's power was nearly wiped out and the battle was lost for him immidiately. However, when Elrond lead Isildur to the Crack of Doom, the only place where the One Ring could be destroyed, Isildur refused to thrust the Ring into the flames (as did Frodo some thousand years later); he was killed in an orc attack on his way to Gondor when the Ring which he was using to make himself invisible (11) slid from his finger (the opposite happened to Frodo at the Prancing Pony when the Ring slid onto his finger by "accident"). All this points out the other side of Sauron's adding an amount of his power to the Ring: He was weakened as soon as the Ring was taken away from him, but the Ring did, to a certain extent, have an "own will" and some power of its own. It betrayed those who wore it, trying to get back to its master, and possessed those who kept it, keeping them from destroying it and forcing them to wear it, which would make them visible to Sauron and the Nazgûl. Those who knew where it was kept developped the wish to own it and even if their intention was to use it against Sauron (which was of course not possible because it was a part if him), their desire to possess it made them betray or kill their friends or even ally with Sauron: Boromir, a warrior from Gondor who was one of Frodo’s companions, tried to take the Ring away from him on Amon Hen, Sméagol, a Hobbit whose people lived in the valleys of Anduin (later known as Gollum), killed his cousin Déagol who refused to give him the Ring and led Frodo into a trap at the pass of Cirith Ungol in order to get back "his precious" and Saruman, one of the Istari, the Maia sent over the sea by the Valar who became known as "Wizards", provided a vast army of orcs for Sauron’s plans of gaining the power over Middle-Earth.
In addition to the power of the Ring, Sauron used the Palántir of the conquered Minas Ithil (Minas Morgul) to force the keepers of the other Palantíri (Saruman and Denethor, also Pippin) to look into them which enabled him to take control over their will.

10 cf. Glorfindel touching Frodo’s wound, TLOTR I/XII, p. 205
11 As Sauron was a Maia and belonged to the spiritual world, any human wearing the Ring would leave the real world and thus become invisible. This is also why the Nine Men became wraiths and why they could see Frodo when he wore the Ring.