"The Rohirrim indeed had no need of news or alarm. All too well they could see for themselves the black sails. For Eomer was now scarcely a mile from the Harlond, and a great press of his first foes was between him and the haven there, while new foes came swirling behind, cutting him off from the Prince [Imrahil]. Now he looked to the River, and hope died in his heart, and the wind that he had blessed he now called accursed. But the hosts of Mordor were enheartened, and filled with a new lust and fury they came yelling to the onset.

"Stern now was Eomer's mood, and his mind clear again. He let blow the horns to rally all men to his banner that could come thither; for he thought to make a great shield-wall at the last, and stand, and fight there on foot till all fell, and do deeds of song on the fields of Pelennor, though no man should be left in the West to remember the last King of the Mark. So he rode to a green hillock and there set his banner, and the White Horse ran rippling in the wind.

"These staves he spoke, yet he laughed as he said them. For once more lust of battle was on him; and he was still unscathed, and he was young, and he was king: the lord of a fell people. And lo! even as he laughed at despair he looked out again on the black ships, and he lifted up his sword to defy them..."

-- Chapter VI, Book Five, Return Of The King

Éomer was orphaned at age eleven when his father Éomund of Eastfold was killed in an ambush near Emyn Muil and his mother Théodwyn of Edoras died soon after. He and Éowyn (then only seven) were sent to Edoras to be raised by Théoden alongside his cousin Théodred, heir to the throne and himself then 24.

After he came of age, Éomer rode as the Third Marshall of Riddermark until Théodred was deliberately murdered by Saruman's forces in battle at the Isen Ford. Disfavored for his insistance on guarding the borders despite Grima-influenced orders to withdraw, Éomer led his men against an orcish incursion which held Merry and Pippin captive, unwittingly facilitating the halflings' escape into Fangorn and triggering the destruction of Isengard by the Ents. He was also the first of his people to meet Aragorn future king of Gondor, and one of the first to accept and respect him.

After Gandalf returned Théoden to his right mind, the king designated his sister-son as his new heir. Éomer fought valiantly at Hornburg, Helm's Deep, Minas Tirith, and Pelennor Fields, where (after Théoden's own death) he became the eighteenth King of Rohan and First of the Third Line of the Kings of Rohan. After the War of the Ring Éomer wed Lothiríel, daughter of Prince Imrahil of Dol Amroth, and their son Elfwine became king of the Mark after him. In memory of his uncle, Éomer was fond of Meriadoc Brandybuck and was visited by both he and Peregrin Took one last time before his death at a ripe old age in Year 63 of the Fourth Age.