Fuinur

Fuinur, which is Sindarin for Shadow Lord, was a Black Númenórean in the Middle-earth legendarium created by J.R.R Tolkien.

Fuinur is mentioned only once, in the passage cited below;

..because of the power of Gil-galad these renegades, lords both mighty and evil, for the most part took up their abodes in the southlands far away; yet two there were, Herumor and Fuinur, who rose to power amongst the Haradrim, a great and cruel people that dwelt in the wide lands south of Mordor beyond the mouths of Anduin. (from "Of the Rings of Power and The Third Age" in The Silmarillion).

His fate is unknown, but Fuinur likely shared Sauron's defeat at the hands of the Last Alliance of Elves and Men.

In the defunct and somewhat obscure Middle-earth Role Playing game from the 1980s, Fuinur is given an extended history. Herumor is then his younger brother.