Who is Mablung from Unfinished Tales of Numenor and Middle-earth and what is their importance?

Mablung is Thingol's captain in "The Tale of the Children of Hurin." It is Malbung who Thingol sends to protect Morwen and Nienor during their search for Turin. When he returns without them, he feels that he has failed and asks Thingol to relieve him of his duties. Thingol claims that no one could have or would have done any better and will not allow him to quit. Mablung is also there when Turin leaves Doriath for the last time.