Tulkas--also called Astaldo, meaning the Valiant--is one of the Valar, named "greatest in strength and deeds of prowess," although he is ranked last of the male Valar. Tulkas' primary purpose for coming to Arda was to make war on Melkor; he didn't even arrive on Arda until well after the other Valar and did so then only to aid them in their battles against Melkor.
Tolkien doesn't allow for much nuance in his depiction of Tulkas in the published Silmarillion. Tulkas is single-minded in his love of fighting and his impatience with peace. He is described as a master of wrestling, contests of strength, and running; he is tireless and needs only his hands for weapons. Likewise, he doesn't ride a horse, since he can outrun even the fastest of them. He lives in the present and is useless as a counselor, although he is described as "a hardy friend." Even in his choice of spouses, Tulkas maintains his singularity of purpose: He marries Nessa, the sister of Oromë, who is described as "lithe and fleet-footed … swift as an arrow," who can outrun even the deer who follow her.
Tolkien provides an uncharacteristically great amount of detail about Tulkas' physical appearance, describing him as ruddy-faced, blond-haired, and bearded (1). Tulkas' resemblance to the quintessential Viking warrior again underscores his rather narrow purpose in the story.
Tulkas' role in the events of The Silmarillion is concentrated entirely in the first part of the book. Once the Noldor leave for Middle-earth, Tulkas is never mentioned again. Prior to this point, however, he plays a pivotal role, and readers frequently see him in action in battles and in councils of the Valar. We are introduced to Tulkas at his arrival, with the explicit purpose of making war on Melkor during his initial conflicts with the other Valar during the shaping of Arda:
But in the midst of the war a spirit of great strength and hardihood came to the aid of the Valar, hearing in the far heaven that there was battle in the Little Kingdom; and Arda was filled with the sound of his laughter. So came Tulkas the Strong, whose anger passes like a mighty wind, scattering cloud and darkness before it; and Melkor fled before his wrath and his laughter, and forsook Arda, and there was peace for a long age. (2)
Prior to Tulkas' arrival, the Valar were being routed by Melkor; Tulkas alone turns the tables on Melkor, bringing him to heel and keeping Arda safe from his destructive influence: Arda's very first superhero. He drives Melkor out into the Void.
Tulkas' arrival and swift drubbing of Melkor established eternal enmity between the two Valar. Melkor explicitly loathed Tulkas (3), and Tulkas' future treatment of Melkor reveals very low tolerance for the dark Vala and even less trust.
Tulkas' proclivity for laughing during battle earns numerous mentions and contributes to his ability to utterly terrify Melkor. Although Tulkas and Oromë are often set side by side as the two he-men of the Valar, Oromë is described as more wrathful, while Tulkas--the stronger of the two--only ever laughs, even when faced with avenging the awesome destruction wrought by Melkor (4).
The peace Tulkas establishes on Arda allows the Valar to go about their work, beautifying the Isle of Almaren, ordering the world, and constructing the first of their great works intended to bring light to the world: the Lamps. Without battle to wage, Tulkas' strength and endurance are put to work instead in the ordering of the world. While his brethren, like Aulë, contribute knowledge and skill, Tulkas gets assigned the grunt work: "the strength of Tulkas had been at the service of all without ceasing in the days of [the Valar's] labour" (5).
While the Valar work, Melkor is mustering his strength and his minions out in the Void. The Valar decide to celebrate their accomplishments, at which point Tulkas and Nessa wed each other. Although declared "tireless" in the Valaquenta, Tulkas' physical and romantic exertions leave him "weary and content," and he falls asleep like a Hobbit after a big meal. Melkor uses this opportunity to hop over the Walls of Night, unseen by the Valar, and begins building Utumno in the north of the world while the Valar look the other way.
Melkor makes his presence known soon enough by toppling the Lamps, causing upheaval of the land and sea that the Valar had so carefully brought to order. Tulkas gives chase, shaking the ruined earth with the force of his pursuit, but is unable to catch Melkor before he slips back into hiding in Utumno; the Valar must spend their strength on trying to save the remnants of the world they've built. Presumably, Tulkas' strength and endurance is required for this task (6).
Melkor's evil continues after the Valar retreat to Valinor. Upset by the damage done to the living land, Yavanna requests the help of the Valar in subduing Melkor, and Tulkas is the first to speak in favor of war--characteristic in his bloodlust and impetuosity--crying out, "Nay! Let us make war swiftly! Have we not rested from strife overlong, and is not our strength now renewed? Shall one alone contest with us for ever?" The Valar do not take his advice: Námo changes the subject by bringing up the impending arrival of the Elves, and Varda gets to work making stars for them. But Tulkas will get his way eventually. Once Oromë discovers the Elves, the Valar decide to take down Melkor for the Elves' sake. Despite the harm that the battle will do to the land, Tulkas celebrates the coming battle.
Indeed, Tulkas triumphs during Battle of the Powers, being the one to throw down Melkor onto his face, bind him, and lead him forth in chains to Aman, where he will spend three ages in the confines of Mandos (7).
After serving his sentence, when Melkor is released, Tulkas is among the Valar who disagree with the decision. Tulkas "clenched his hands whenever he saw Melkor his foe go by; for if Tulkas is slow to wrath he is slow also to forget," although he abides by Manwë's decision in an effort to prove the effectiveness of obedience by being obedient himself, a choice that, of course, has disastrous consequences. Among other things, while the Valar like Tulkas capable of perceiving Melkor's evil remain silent, Melkor sows the seeds of discontent in the House of Finwë; when Melkor is revealed as the cause of the animosity between Fëanor and Fingolfin, it is Tulkas who is once again sent forth to bring Melkor to justice. Yet again, Melkor evades Tulkas by hiding, disguising himself as a cloud in the hills; when brute strength is not required, Tulkas does not easily dominate, and Melkor is an exceedingly cunning foe. Tulkas returns empty-handed (8).
Melkor comes next to Fëanor's gates in Formenos. When Fëanor sends him away, Finwë sends a messenger to the Valar, and Tulkas again goes out in pursuit of Melkor. And once again, Melkor disguises himself--this time as a stormcloud--and avoids capture. After destroying the Two Trees, Melkor flees again in a cloud of darkness caused by Ungoliant, and here he overpowers Tulkas physically as well as mentally. Tulkas is unable to proceed in the dark: "Tulkas was as one caught in a black net at night, and he stood powerless and beat the air in vain" (9).
This defeat is the last time we see Tulkas really and truly in action. In the next chapter, the Valar propose to Fëanor that he use the light in his Silmarils to rekindle the Two Trees. In a typical show of impatience (and a complete lack of understanding of what he asks of Fëanor), Tulkas demands, "Speak, O Noldo, yea or nay! But who shall deny Yavanna? And did not the light of the Silmarils come from her work in the beginning?" (10). Tulkas is not mentioned again in The Silmarillion save by Fëanor: While rousing the Noldor to action, he says of the Noldorin vengeance on Melkor, "For we will go further than Oromë, endure longer than Tulkas: we will never turn back from pursuit" (11). Whether conquered irreparably by his oldest foe or because the point of view shifts from Valinor to Beleriand, we do not hear of Tulkas again, even during the War of Wrath, when he presumably would have played a leading role.
Unlike many of the Valar, from the earliest drafts of The Silmarillion, Tulkas existed more or less in the form we find him in the published Silmarillion, although Tolkien enriches his character with far more detail and nuance. The Book of Lost Tales describes him as "lusty" and a "perpetual youth." Like his character in the published book, he dislikes Melkor from the start, delights in physically dominating him, and intimidates (and, because of that, earns the hatred of) the dark Vala.
Similarly, as in the published book, Tulkas is associated with Aulë during the building of Arda. Tolkien provides us with more detail, describing how Tulkas helped Aulë bring marble, metal, and stone to Valinor to aid in the construction of the two cauldrons that water the Two Trees. After the Trees create light to work by, Tulkas continues to aid Aulë, a connection that seems to have been lost between the Lost Tales and the published book, where Tulkas becomes known most for his physical strength, while Aulë's role as the patron of the scientists and technologists among both Ainur and Eldar sets him apart from Tulkas' brute approach.
Tulkas' playfulness is also emphasized in the Lost Tales as it is not in the published Silmarillion. It is said that
… he dwelt amidmost of Valmar. Most youthful is he and strong of limb and lusty, and for that is he named Poldórëa who loveth games and twanging of bows and boxing, wrestling, running, and leaping, and songs that go with a swing and a toss of a well-filled cup. Nonetheless is he no wrangler or striker of blows unprovoked as is Makar, albeit there are none of Valar or Uvanimor (who are monsters, giants, and ogres) that do not fear the sinews of his arm and the buffet of his iron-clad fist, when he has cause for wrath. His was a house of mirth and revelry; and it sprang high into the air with many storeys, and had a tower of bronze and pillars of copper in a wide arcade. In its court men played and rivalled one another in doughty feats, and them at times would that fair maiden Nessa wife of Tulkas bear goblets of the goodliest wine and cooling drinks among the players. (12)
Tulkas' association with the Vala Makar--who along with his sister Meássë represent a Norse contingent among the Valar, and neither of whom survived beyond the Lost Tales--is an interesting one, as it seems that Tulkas took on some of Makar's qualities when Makar was removed from the story. In Lost Tales, it is said that Tulkas is the only Vala who will journey near Makar's halls and contend with the warriors there so "that he might not grow soft in his fair living" but that he was not friends with them, who were inclined to favor Melkor (13). Although Tulkas' animosity toward Melkor appears even in this earliest draft, his impetuosity and bloodlust--qualities that belong to Makar in the Lost Tales--are not yet as obvious. In the Lost Tales also, Tulkas does not arrive late to Arda, as he does in the published Silmarillion; it is Makar who enters Arda after all of the other Valar. As The Silmarillion evolved, Tolkien shifted the Valar more toward dualist poles of evil and good: Melkor in the evil camp and the rest of the Valar, having lost any residual creepiness or moral ambiguousness present in the Lost Tales, on the side of Ultimate Good. This left no room for a character like Makar, although Tolkien seems to have shifted his traits somewhat onto Tulkas and sanitized them to create a blindly obedient warrior seemingly incapable of independent thought.
The Lost Tales also cast Tulkas in a different and more prominent roles in the capture of Melkor. In this early version, the Valar trick Melkor rather than overthrowing him with force alone, agreeing to send Tulkas in wrapped in chains to kiss Melkor's foot. Tulkas does indeed enter Utumno in chains, but he leaps free of them and, with Aulë and Oromë, overpowers Melkor and brings him forth for sentencing. After Melkor's term in Mandos, he is additionally sentenced to "for four ages yet dwell as a servant in the house of Tulkas, and obey him in requital of his ancient malice" (14). This sentence is mentioned several times throughout the Tales as having been carried out.
In this earliest version of the story, a renegade messenger comes from Mandos, bearing a message from Melkor. Tulkas defies Manwë and leads others of the Valar in hurling this messenger from Taniquetil to his death, quite a contradiction of the character who in the published Silmarillion would say nothing against Melkor's freedom out of obedience to Manwë. The connection between Aulë and Tulkas is again emphasized as the two pledge to fill in the gap in the mountains through which Melkor passed, and also when the two attempt to retrieve the final fruit of the ruined Trees. We do see the published story taking shape as Tulkas and Melkor battle on the plains of Valinor after the Darkening of the Two Trees, and Melkor repeatedly fools Tulkas by disappearing into a fog right as Tulkas is about to wound him. (14, 15)
Like many of the Valar, Tulkas began his existence in the Lost Tales as a character far richer in detail and nuance. As Tolkien shifted his story toward moral dualism later in his life, Tulkas' character shifted as well, becoming singular in his strength, warlust, and impatience rather than the playful, youthful Vala simultaneously capable of deceit, disobedience, and merciless violence.