Mithrandir believes that Ayorzén's knowledge of Mordor might be made useful by those who adventure within its bounds.
'Mordor has been closed to the eyes of Gondor for more than a thousand years, ever since the fall of Durthand and the expulsion of the Thandrim. What transpired beneath the shroud of Gorgoroth remained unknown to us, and it brewed a bitter cup of rumour, and worry, and fear. That was in aid of Sauron's plans, as ever, for he knew the uses of fear better than any creature in this Middle-earth.
'But we have one in our keeping who witnessed the last days of the War of the Ring from the other side. Ayorzén walked in Mordor when the peoples of Gondor and indeed of all Middle-earth could not pass the bounds of that land. What did he see? What does he know? He claims he was involved in high councils of war. Perhaps that is true, and perhaps it is not, but there is no question that he may have knowledge of Sauron's lieutenants that we simply do not.
'Can he be forgiven of his crimes? If he can be so forgiven, he might be given a new life in Gondor in exchange for the information he possesses about Mordor and the power structure in the Black Land after the downfall of Sauron. Speak to Aragorn. It must be he who will forgive Ayorzén of these crimes, if any will.'
Ayorzén has given you the names of especial terrors in Mordor, and wants you to speak those names to some of the freed Nurnhoth at the Black Gate.