Anborn, like Mablung and Damrod, is another of Faramir's troops. He reports to Faramir that they have not been followed by orcs on their way to Henneth Annûn, but there is something strange tailing them, "like a shadow on the ground, and it whisked behind a tree-trunk when I drew nigh and went up aloft as swift as any squirrel could" (4.5.94). Anborn is the one who watches over Gollum with his arrow nocked when Faramir is arguing with Frodo for Gollum's life. Anborn is also the one who catches Gollum by the nape of his neck and ties him up, awaiting Faramir's decision about his life.
Sam makes a passing reference to Beren when he reminds Frodo, "Beren now, he never thought he was going to get that Silmaril from the Iron Crown in Thangorodrim, and yet he did" (4.8.61). This is a reference to Tolkien's own larger mythology for Middle-earth, as contained in the Silmarillion. For more on Beren and his lady-love Lúthien Tinúviel, see our "Character Analyses" in our The Fellowship of the Ring learning guide.
Brego is the son of Eorl the Young. He builds Meduseld, the Golden Hall at the center of Edoras in Rohan.
Ceorl is the lone Rider who comes to inform the Eorlingas, Théoden's host of troops, that all of the remaining forces of Rohan have been marshaled in the fortress of Helm's Deep by Erkenbrand of Westfold. At Ceorl's news, Théoden makes the decision to ride to Helm's Deep to relieve Erkenbrand.
During the days of this Steward of Gondor, the people of Gondor made an alliance with the Rohirrim (and specifically, with Eorl the Young). When the Rohirrim rode to help Gondor in battle on the Field of Celebrant, they drove out the enemies of Gondor who had occupied their northern provinces. In exchange, Cirion ceded to the Rohirrim the fields of Calenardhon, which is now called Rohan. They have been true allies of Gondor ever since.
Denethor is the Steward of Gondor and current Lord of that kingdom. He is the father of Boromir and Faramir. We don't get much sense of what he is like in The Fellowship of the Ring or The Two Towers. All we know is that Faramir and Boromir have this guy as a dad. More to come in The Return of the King.
King Eärnur is the last of the line of Anárion, Isildur's brother. Anárion left an heir, Meneldil, whose sons ruled Arnor until the end of that kingdom in the north (for more on these complicated descent lines, check out our "Character Analyses" in The Fellowship of the Ring learning guide). King Eärnur was lord of Gondor, but he was childless when he went to war and never came back.
With the death of King Eärnur, the line of Anárion was lost. Obviously, the line of Isildur was busy running around in the forest being Rangers (until Aragorn, that is). So King Eärnur's death left his steward Mardil in charge of the kingdom of Gondor until the heirs of Elendil should return to the throne. It has now been roughly a thousand years since the fall of Eärnur (see The Return of the King Appendix B: "The Tale of Years"), and Denethor is the twenty-sixth Steward to rule Gondor in the absence of the king.
Elendil is Aragorn's ancestor, a Man of Westernesse, of the line of Númenor, and the father of the last two Kings of Arnor (to the north) and Gondor (to the south), before Aragorn's return to power. Elendil died fighting Sauron during Sauron's rise in the Second Age. He was a member of the Last Alliance between Men and Elves, along with the Elven-king Gil-galad.
Elfhelm, like Grimbold of Westfold, is a soldier whom Gandalf sends with many Riders of Rohan to Edoras to protect the city after the Battle of Helm's Deep. Gandalf comforts Théoden that Meduseld will still be standing after these wars with Saruman.
Éomund is Éomer's (and Éowyn's) father. Aragorn also reveals that he once rode with the men of the Riddermark, "though under other name and in other guise" (3.2.75), which tells us he knew Éomer's father. With this assurance that Aragorn is not a stranger to Rohan, Éomer lets Aragorn, Legolas, and Gimli pass on to save Merry and Pippin.
Eorl the Young is the ancestor of the Rohirrim, the Riders of Rohan. He is related to the Bardings of Dale and the Beornings of the Wood (see The Hobbit and The Fellowship of the Ring.) Aragorn specifies that the Riders, Eorl the Young's descendants, are "men tall and fair" who "will not love the Orcs" (3.2.99), which is a comfort.
Eorl the Young is the subject of the lament Aragorn sings as they pass the burial mounds of King Théoden's people: "Where now the horse and the rider? Where is the horn that was blowing? [...] They have passed like rain on the mountain, like a wind in the meadow" (3.6.15). Eorl the Young also appears in a rich tapestry hanging in Meduseld, the Golden Hall of Théoden. He is riding to the Battle of the Field of Celebrant. (The Celebrant is the river that flows out of the Nimrodel in Lothlórien; in Common Tongue, it is called the Silverlode [The Fellowship of the Ring 2.6.65].)
The Battle of the Field of Celebrant is the fight that cemented the alliance between Rohan and Gondor. The Rohirrim joined the men of Gondor in driving out their enemies, who had occupied the northern provinces of the kingdom. In exchange for their help, Cirion the Twelfth Steward awarded the Rohirrim these lands, the fields of Calenardhon, for their own. So these provinces to the north of Gondor have become Rohan.
This decision to award the fields of Calenardhon to Eorl the Young is also the main bone of contention that Saruman uses to whip up the wild men of Dunland against the Rohirrim in The Two Towers. The Dunlanders have always felt these northern provinces should have been theirs. Saruman is exploiting an ancient grudge to serve his own purposes. However, thanks to the decision of Eorl the Young and Cirion the Twelfth Steward, the men of Rohan "became [Gondor's] allies, and have ever proved true to [Gondor], aiding [Gondor] at need, and guarding [Gondor's] northern marches and the Gap of Rohan" (4.5.121).
Éothain is a member of Éomer's host of riders; as Éomer chats with Aragorn, Éothain tells his captain to get a move on: "Time is pressing [...] We must hasten south, lord. Let us leave these wild folk to their fancies. Or let us bind them and take them to the king" (3.2.141). Éomer tells Éothain to shut up. But later on, when Éomer passes horses to Aragorn, Legolas, and Gimli, Éothain protests that Gimli shouldn't receive a horse of the Mark. Gimli agrees to ride behind Legolas, because he doesn't feel comfortable on horses anyway.
Erkenbrand is the genius who gathers together those troops who have been scattered by marauding orcs to his "fastness in Helm's Deep" (3.7.9). (Helm's Deep is in the White Mountains between Isengard and Edoras, the king's city in Rohan.) When the Eorlingas, the king's forces, reach Helm's Deep under the command of Théoden, they do not find Erkenbrand waiting for them. They believe that he and his remaining men have been killed, leaving only a few men of the Helm to defend that fortress.
But as the king fights to hold this stronghold through a day and night, Gandalf comes with Erkenbrand and his forces (oh, and a forest of very angry trees, too) at dawn to beat back the orcs and wild men of Isengard. Between Théoden King and the troops of Erkenbrand, the men of Rohan hold Helm's Deep against Isengard's forces. Erkenbrand's shield is red, and he is "tall and strong" (3.7.158), as you would expect, since all of Tolkien's soldiers are.
Gamling is the old veteran who is manning Helm's Deep when Éomer, Théoden, and the Eorlingas arrive with reinforcements. He is the leader of the Helmingas, the soldiers of the Helm. He is relieved to see the Eorlingas, since "most of [his soldiers] have seen too many winters, as I have, or too few, as my son's son here" (3.7.45). He also assures Théoden that they have a huge store of food in Helm's Deep, which is lucky since the orcs are burning Rohan's farmland; at least they don't have famine to worry about.
Gamling helps Aragorn and Éomer hold the Hornburg against the orc onslaught, but his men are tiring—what should they do? What they do, of course, is wait for Gandalf to arrive at dawn. Gamling survives the battle of Helm's Deep, and is at Éomer's side when all the major characters come together after the battle.
A deceased member of Éomer's host; it is his horse, Hasufel, whom Éomer gives to Aragorn.
Grimbold of Westfold is a soldier of Rohan. When Gandalf finds him near Isengard, he sends some of the scattered Riders of Rohan with him to join Erkenbrand at Helm's Deep after the battle.
One of the ancestors of the Númenoreans, the Men of Westernesse, in the days when elves and men were not so distant as they are in the Lord of the Rings cycle. Faramir points out that, in the olden days, "the Edain, the Fathers of the Númenoreans, fought beside the Elves in the first wars, and were rewarded by the gift of the kingdom in the midst of the Sea, within sight of Elvenhome" (4.5.126). In Middle-earth, this close friendship between humans and elves is no longer present, but the fact that Hardor the Goldenhaired is also named Elf-friend shows the importance of this early alliance between humans and elves to the Men of Númenor.
Isildur is one of Elendil's two sons, and it is through Isildur's line that Aragorn is descended from the Kings of Gondor. After Elendil's death, it is Isildur who "cut off the finger of the Enemy" (4.3.36) during the war of the Last Alliance and took the Ring of Power for himself. For the full story of what happens to Isildur as a result of this decision, check out our "Character Analysis" in our The Fellowship of the Ring learning guide.
For the purposes of The Two Towers, Isildur is mainly important because he is the one who builds Minas Ithil, the Tower of the Moon, in the mountains of Ephel Dúath after Sauron's fall. And of course, this is where Gollum leads Frodo and Sam when they try to get across to Mount Doom. Also, Faramir is extremely interested in "Isildur's Bane" (4.5.3), that is, the Ring—but that has less to do with Isildur himself, and more to do with its power to corrupt his brother, Boromir.
Mablung and Damrod are the two guards whom Faramir leaves with Frodo and Sam as he continues his scouting mission for the Southrons. As Frodo listens to them speak quietly, he realizes that among themselves, they speak Elvish or something very like it. This marks them as the Dúnedain of the South, descendants from the Men of Westernesse much like Aragorn's Rangers in the North. Their forefathers lived in Ithilien before it fell to Mordor.
Now, Lord Denethor, Steward of Gondor, employs them to cross the Anduin and conduct a kind of guerilla warfare on the orcs and other enemies between the river and the mountains of Ephel Dúath. Damrod and Mablung stand with Frodo and Sam as they watch the battle playing out between Faramir's crew and the Southrons. When the oliphaunts appear, it is Damrod who sees them first: "May the Valar turn him aside! Mûmak! Mûmak!" (4.4.100).
Mardil is "the good steward" (4.5.59) who looked after the Kingdom of Gondor when its last king, King Eärnur, died in battle without an heir. Lord Denethor, Boromir, and Faramir are all descended from Mardil.
Théodred is the son of Théoden King. He was killed by orcs five days before the arrival of Aragorn, Legolas, Gimli, and Gandalf in Rohan. He was the Second Marshal of the Mark, just as his cousin Éomer is the Third.