Egalmoth was one of the lords of Gondolin, the mighty hidden city of the First Age. We know he was Noldorin, but we don’t know if he was born in Valinor before the exile of the Noldor, or born in Middle Earth afterwards (to be a lord of Gondolin, I’d assume that he was born in Valinor, but we don’t know for sure.)
His physical characteristics aren’t described, but as one of the Noldor it’s likely that he had dark hair and dark eyes. He wore a blue mantle with crystal stars on it. He was very talented with a bow, but he also carried a sword - in fact he is the only Noldo known to carry a curved blade.
Egalmoth’s house was the House of the Heavenly Arch, which was a very wealthy house known for their many jewels. Their shields were blue with a jewel in the center built of seven gems (rubies, amethysts, sapphires, emeralds, chrysoprases, topazes, and amber), creating a rainbow effect. They mostly defended the northern wall of the city during its attack.
Egalmoth actually survived the fall of Gondolin, escaping with Tuor and a few survivors from his house. They made it to the Havens of Sirion, where they lived in relative peace until the Third Kinslaying (when Feanor’s sons attacked the Havens after Elwing refused to give them the silmaril.) Egalmoth was killed in this battle.
SOURCES: The Silmarillion, The Lost Tales Part 2 (“The Fall of Gondolin”)