Tolkien described Saruman as an old man with white hair and a long white beard. He was tall, his face was long, and his eyes were deep and dark. He would appear in a hooded white cloak; later, he changed into a cloak that changed colours as he moved.

He was not actually a Man or even an Elf, but a Maia clothed in flesh. As such, he was immortal and extremely powerful, yet he had limits on how far these powers could be used. His two most salient powers were his knowledge and his voice.

Knowledge of the deep arts was of particular interest to him, especially when relating to power such as the Rings of Power and the far seeing palantíri. He was also deeply learned in ancient lore regarding powerful kingdoms such as Númenor, Gondor and Moria. His voice and speech were extremely convincing, more powerful than mere rhetoric. When he focused this power on a person or a group of people, he could sway their hearts, plant fears and sow lies as he pleased. Depending on the willpower of the listener, this spell could last as long as the speech did, or it could take root in them and last forever. Other powers include knowledge of machinery and chemistry, probably inseparable from explicit magic. An instance of this includes the "blasting fire" employed by his Uruk-hai army in the Battle of the Hornburg, which was probably some kind of explosive. Machinery and engines characterized both his fortified Isengard and his altered Shire. In this, he probably sought to emulate Sauron.

His science also extended to biological areas. He crossbred Men and Orcs, creating both 'Men' with orc-like vileness and treachery and 'Orcs' with human size and cunning. His Uruk-hai, Orcs unafraid of daylight, are often speculated to have been examples of the latter. Likewise, his human spies in Bree were said to have Orc blood. He also employed birds in his service, although this might be attributed to Radagast the Brown, ordering them to report to Orthanc, Saruman's stronghold.
Saruman resembled Gandalf not only in appearance but originally also somewhat in character, but unlike Gandalf, Saruman was proud. He saw himself as the most powerful of the Istari, expressing clear contempt for Radagast the Brown. Saruman was no fool: he realized Gandalf's power and eventually came to see him as an equal and later as a superior, much to his distress. He began to become jealous of Gandalf, eventually convincing himself Gandalf must be scheming against him, to justify his own scheming against Gandalf and the rest of the White Council. Being regarded as more powerful than Gandalf before Gandalf's "rebirth", it is a common assumption he would also wield explicit magic similar to Gandalf, including using artificial light, locking spells, or creating fire. Saruman likely was true to his mission in the beginning and actually believed in working to stop Sauron, but his pride and later arrogance (as well as his jealousy towards Gandalf) turned him into a traitor to the cause he had once served. Saruman's betrayal was not sudden but slowly grew over time, until at last he had convinced himself that he could not have taken any other path. This false belief kept him from taking his last chance at redemption. Because he must have realised this, he only became more bitter, blaming Gandalf more than anyone else for his own downfall.

The name given to him by Men, Saruman, is in the Westron language. In Tolkien's works, this language is almost never shown directly but translated into English and Anglo-Saxon forms. In this case, Tolkien used the Anglo-Saxon root word searu which means "skill" or "cunning". The real Westron version of his name remains unknown. His name among the Elves is Curunír, which is in Sindarin, a language Tolkien did not translate. It means "man of skill", and was often followed by Lán, which means "white". In Valinor, his name was Curumo, which is the Quenya version of the same name. His name given by the men in the Cleansing of the Shire, Sharkey is a bastardisation of the Orcish Sharku which means Old Man.

In Valinor, the land of the Valar, a council was called by Manwë, leader of the Valar, shortly after the defeat of Sauron by the Last Alliance. Through Sauron was overthrown, it would later turn out that he had not been effectively vanquished and his shadow began to fall upon Middle-earth a second time. It was decided to send five emissaries to Middle-earth. These should be "mighty, peers of Sauron, yet forgo might, and clothe themselves in flesh", as they were intended to help men and elves unite against Sauron, but the wizards were forbidden from matching the Dark Lord in power and fear. One of those who went was Curumo (Saruman), a powerful Maia of Aulë, just as Sauron was. Maiar were angelic creatures of the same kind as the Valar, only of lower order. Together, they were the Ainur, and existed before the Arda, the world, was created.

Saruman was one of the Istari who volunteered to go to Middle-earth, whereas the last one, Olórin (Gandalf), was commanded by Manwë to go. Varda said of Gandalf the Grey, who went as the third Istar, that he was "not the third". Saruman also eventually discovered that Círdan the Shipwright had given Narya the Red Ring to Gandalf upon their first landing in Middle-earth. Even though Saruman was immediately considered the head of the order while Gandalf was considered the least, Círdan had divined in Gandalf as the wisest and greatest of the wizards. Saruman's jealousy of Gandalf had grew from these events, perhaps because he feared that the Grey would eventually supplant him. Saruman was also commanded to take Radagast with him, against his will. This may have contributed to his contempt for him. They travelled to Middle-earth with two other Istari, Alatar and Pallando, known as the Blue Wizards. The five wizards arrived at the Grey Havens in the west of Eriador around the year 1000 of the Third Age. Only the keeper of the havens, Círdan, knew Saruman's identity and origin. Saruman and the two Blue Wizards went into the east of Middle-earth. After one and a half millennia, he returned to the west, just as Sauron's power was growing again in Dol Guldur.
When the White Council was formed at approximately year 2463 of the Third Age, Saruman was appointed its leader, though Galadriel wanted Gandalf in this position. At this point Saruman had begun to sense the resurgence of Sauron and to envy and desire his power, and especially his One Ring. This was also the same year that the One Ring was found by the halfling Sméagol, who would later be called Gollum.
In the year 2759 T.A., Saruman settled in Isengard with the permission of the Steward of Gondor, Beren. The stronghold was by then abandoned by Gondor. There he became important in the informal alliance defending the west of Middle-earth. In the tower of Isengard, Orthanc, he also found one of the remaining palantíri.
In 2850 T.A., Gandalf entered Dol Guldur and confirmed that the evil presence was indeed Sauron. By Saruman's advice, the White Council decided against attacking Dol Guldur. Gandalf would later remark that it was at this council-meeting that he first began to suspect that Saruman desired to possess the One Ring. Saruman's real intention was to permit Sauron to build up his strength, so that the One Ring would reveal itself. He later found that Sauron had more knowledge of the possible location of the One Ring than he expected, and in 2941 T.A., he finally agreed to attack Dol Guldur.

When Sauron abandoned Dol Guldur, he took up his reign in Mordor and declared himself openly. He established contact with Saruman through the palantír captured from Minas Ithil, now Minas Morgul. Saruman succumbed to Sauron's will and became in secret a reluctant subject of Mordor. When Gandalf presented Saruman with the discovery and the location of the One Ring, Saruman revealed his desire for it and his alliance with Sauron. When Gandalf refused to join with him, he held him captive in Isengard. Gandalf later escaped with help from Gwaihir the Windlord and made Saruman's treachery known to the rest of the White Council.

Saruman also betrayed Sauron by lying to the Nazgûl, who were searching for Baggins, who had found the One Ring years before. He pretended to know nothing, but the Nazgûl later captured one of his Shire spies. Believing that he would find no pity from either quarter (a false assumption, since he was later offered pardon by Gandalf), Saruman now put all efforts into obtaining the One Ring for himself. Not all of these efforts ever became clear, but they included sending spies to waylay Frodo Baggins on his flight from the Shire, attacking Rohan outright with Uruk-hai and dispatching raiding parties of Uruk-hai accompanied by Mordor Orcs on likely routes the Fellowship of the Ring might take to Gondor. One of those parties captured Peregrin Took and Meriadoc Brandybuck after peppering Boromir with arrows as he tried to defend Pippin & Merry, which led Aragorn, Legolas & Gimli on a search which eventually led them to the breaking of Isengard by the Ents under Treebeard.

His plans failed, and Saruman suffered a series of setbacks. Saruman's Shire network did not capture Frodo Baggins; Gandalf rallied Rohan to victory; Éomer stopped his only partially successful raiding party; and control of Isengard was lost to the Ents. Confined to Orthanc and utterly defeated, Saruman made one final attempt to turn Théoden and Gandalf, which failed and cost him his staff. He lost the palantír of Orthanc when Gríma Wormtongue threw it of a balcony of Orthanc, undecided about hitting Saruman or Gandalf. Left out of the final stages of the War of the Ring, he eventually managed to convince the Ents who kept him captive into letting him leave Isengard after he met the conditions of handing over the keys of Orthanc. He then went to the Shire, which his agents lead by Lotho Sackville-Baggins had brought under control. Spending his final days as a small-time thug lord in Hobbiton known as Sharkey, where he enslaved the Hobbits, he was eventually betrayed and killed by his own servant Gríma Wormtongue on November 3, T.A. 3019, after the Battle of Bywater, where the Hobbits had Saruman's thugs surrounded with many Took bowmen, and as the thugs tried to fight their way out, they were shot.
Saruman, being a Maia, did not truly die. His spirit separated from his body much like Sauron's after the Downfall of Númenor. As a discorporated spirit, he should have been called to Mandos, but the tale implies that he was barred from returning. Tolkien indicated that his spirit was left naked, powerless and wandering in Middle-earth.

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