'The text you recovered told of a goblin warrior, a champion of Angmar that commanded a legion of his kind.
'Is this a legend of old or are these the words of truth? That I cannot say, but this Mordirith's servants are many and powerful...I do not doubt these claims.
'You should investigate the matter. Return to Minas Maur and strike its gates. Should this fabled champion exist, it would be ill-advised to ignore such a challenge.'
Background
Lindir translated the text you found from the Black Speech into Westron.