Elrond is an elf lord and lives in Rivendell (Lord of the Rings, Fellowship of the Ring [volume I], Book 2). The valley of Rivendell is under his power, including the river which swept away the black riders when they tried to catch Frodo when he crossed the river to enter Rivendell. As Lord of Rivendell, Elrond is mighty among both Elves and Men.
Elrond was the herald of Gil-galad. He was one of the three present when Isildur cut the ring of power from the Dark Lord’s (Sauron’s) hand. The company to destroy the One Ring was formed in Rivendell. While Elrond appointed many of the company, he did not appoint them all (Frodo and Sam appointed themselves).
Elrond wears Vilya, a gold ring set with a blue stone (a sapphire), the mightiest of the three rings of the Elven-Kings made by Celebrimbor and the Mírdain of Eregion in the middle years of the Second Age. It was also known as the Ring of Air.