Glorfindel was a lord of the House of the Golden Flower, one of the noble houses of Gondolin, golden-haired and mighty among the Eldar. In the Fall of Gondolin, as he led a part of the fleeing refugees up the high pass of Cirith Thoronath, a Balrog fell upon them out of the mountains; Glorfindel fought it alone upon a pinnacle of rock and cast it down to ruin, but was himself dragged into the abyss by his foe, and so perished defending the survivors -- among them the child Earendil. The Eagle Thorondor bore up his body, and it was laid in a mound on which yellow flowers ever after bloomed.
So great were his valour and purity that, alone among the slain of that age, Glorfindel was released from the Halls of Mandos, rehoused in living form, and permitted to return to Middle-earth -- in the Second Age, it is thought -- with power and grace enhanced by his long sojourn in the Blessed Realm. In the Third Age he dwelt with Elrond at Rivendell, one of the mightiest Elf-lords left in the world, who lived at once in the seen and the unseen realms and shone against the wraiths with the light of Aman. It was Glorfindel who rode out and bore the failing Frodo on his horse Asfaloth in the flight to the Ford of Bruinen; and it was of him that the prophecy had long before been spoken that the Witch-king of Angmar would not fall by the hand of man.