The Champion of Minas Angos
'The text you recovered spoke of the betrayal of the Longbeards by the Dourhands, and of a champion that survived the death of his master, the pale dwarf called Skorgrim.
'I remember this dark day but is this evil champion the stuff of legend? 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 Angos and strike its gates. Should this fabled champion exist, he would be ill-advised to ignore such a challenge.'
Lindir translated the text you found from the Black Speech into Westron.
Summon and defeat Minas Angos' Champion