Gildor

Gildor Inglorion is a protagonist in the first book of The Lord of the Rings trilogy, he is an Elf descended from Finrod, who lived in the First Age of the Sun. Gildor supports Frodo and the Quest (albeit unknowingly, as he doesn't know Frodo has the Ring or is going to Mordor) in the first part of the book. He is one of Frodo's first allies.

History
Gildor was presumably born in the First Age of the Sun or after. Being an Elf, he is immortal although he can be killed. However, unlike other Elves, Gildor does not seem to be warlike or a warrior. He is merely a traveller, and is planning on leaving Arda like all the other Elves to go to Valinor.

The Fellowship of the Ring
Gildor first appears when Frodo, Sam and Peregrin Took are lost when venturing outside the Shire and have just had an unpleasant run-in with the Black Riders. Gildor notices the Hobbits sheltering under the tree when the Black Rider did not, and Gildor calls out to the other Elves how unusual it is to see Hobbits here, so far from the Shire. They say Hobbits are dull folk and they do not really want their company. However, when Peregrin mentions the Black Riders, asking the Elves to explain what they are, Gildor gets interested and alarmed. He asks why they'd want to know of such evil creatures, Peregrin says one or two Riders overtook them and they are being followed. Gildor then says he shall shelter them at his camp that night, amazing Sam who has always been a big fan of the Elves.

At the camp, the stars rise, and the Elves admire their favourite constellations. In the camp, which is more like a mead hall, the Elves welcome the Hobbits and give them a good yet simple dinner. Then they explain that the Black Riders are just a great evil too terrible to talk about and the Hobbits should avoid them if possible.

Gildor does say, however, that the time may come when Frodo knows more about the Black Riders then he, Gildor does. Gildor also reveals he knew Bilbo well and met him several times, once in this very hall when Bilbo left the Shire for good. Gildor says that Hobbits are curious creatures and show great strength at times. Gildor tells Frodo he knows Frodo will reach Rivendell and meet Bilbo again. He also says that he will send word to the other Elves he encounters and Lord Elrond knows of their journey. After giving Frodo Elbereth's protection, Frodo grows tired and decides to sleep. Gildor then escorts Frodo to the dormitory and he sleeps with the other two Hobbits.

In the morning, Gildor has left to finish his journey and to tell the other Elves of Frodo's coming. Sam says Peregrin didn't want to leave Frodo any of the luxurious Elvish food but Sam insisted.

The Return of the King
Gildor may have been amongst the wedding guests who came to Minas Tirith when Aragorn got crowned as Elessar. However, this is not confirmed. It is known a huge crowd of Elves from Rivendell got invited.

Gildor returns at the climax when the War is over and Sauron defeated. Gildor knows Middle-earth is now at peace under Elessar so he departs with Frodo and Gandalf on a boat to Valinor and lives there at peace to this day.