Aragorn believes that you learned two useful pieces of information from Dulgabêth that should guide your further adventures in Gorgoroth.
'I believe you learned two useful pieces of information from Dulgabêth. The first is this: the forces of Mordor are not unified, and they might be turned against one another. Indeed, they may already be doing so on their own, without our assistance! He seems most concerned about his rival, who sent forces to reinforce Cirith Ungol. This rival is the one he called Ugrukhôr, the Captain of the Pit, and I have heard tell of him before. He is cruel and without mercy, and it was he who promised the Thandrim of Durthand peace and gave them slaughter instead.
'The second piece of information Dulgabêth unwittingly gave to us might not be as immediately useful, but still I want to learn what it signifies. He spoke of the Gúrzyul, and the name makes me uneasy for its evocation of the Nazgûl. The Nine are slain, destroyed alongside Sauron, and few could rival them in malice or power, but we should tread carefully near any reminder of them.
'I understand that Ayorzén the Wily refused my offer of a place in Gondor, and has been haunting the pass of Cirith Gorgor just inside the Black Gate. See what he makes of the information we have learned, ${PLAYER}, and follow that knowledge where it leads.'
Ayorzén the Wily is in Cirith Gorgor, just inside the Black Gate.
Mithrandir has asked you to follow both of the leads you have uncovered, accompanying Atli into Lhingris and Harthalín into Talath Úrui.