You have pledged to lend your aid and your adventuring skills to Durin's Folk and fight on their behalf in Mordor.
'I am pleased that you have pledged to aid Durin's Folk as we adventure in Mordor, ${PLAYER}! Who knows what treasures were wrongfully stolen from us, and now wait to be reclaimed and restored to their rightful owners?
'My adventuring days are not yet done. My captivity by the Dourhands in the North Downs has taught me the value of caution, and I will exercise it smartly. See that you do as well, my valiant friend, for the land of Mordor is a place of evil, Dark Lord or no!
'But before you begin to adventure on behalf of Durin's Folk, you should return to Erebor and speak with the King under the Mountain! That title belongs now to Thorin III, for his father Dáin fell before the gates of Erebor during the Battle of Dale. He died well, but now the responsibility of leading the dwarves falls to his son. Go to the Hall under the Mountain, in Erebor, and present yourself to him. He will be glad to have your service!'
Thorin III is now King under the Mountain, and rules Durin's Folk from Erebor. Now that you have pledged to aid the dwarves as they adventure in Mordor, Dori believes you should meet with Thorin at the Lonely Mountain.
King Thorin is currently meeting with his advisors, and is not free for an audience. Foldgráf recommended that you make yourself familiar with the Hall under the Mountain while you wait.
King Thorin should now be ready to meet with you.
Thorin III, King under the Mountain, is at his throne in Erebor. You should present yourself to Hrostyr, his personal guard.
Three adventuring dwarves stand by the throne in the Hall under the Mountain. They have been charged by King Thorin III with the same task as you.