Norren was the Maester of Maidenpool during the Dance of the Dragons and served House Mooton loyally. He was maester to both Lord Walys Mooton and his brother, Lord Manfryd Mooton. Norren was a young maester, aged only 22.
House Mooton allied with Rhaenyra Targaryen during the Dance of the dragons, and Lord Manfryd hosted King Daemon Targaryen and Nettles, a baseborn dragonrider and Daemon's paramour, during the first stage of their operation in The Riverlands. Rhaenyra grew skeptical of Nettles after the betrayal of two of her other baseborn dragonriders and ordered her death, along with that of Ser Addam Velaryon.
A message is sent to Maidenpool instructing Lord Manfryd to kill Nettles, but spare daemon. Manfryd doesn't want to follow through on this request as he doesn't want to break guest right or incur the wrath of daemon and his dragon. Instead Norren suggests that manfryd pretend to have never seen the note, lifting him from the responsibility.
Instead of killing Nettles Norren shows the note to Daemon, who calls him a bad maester but a good man, and leaves with Nettles the next day, setting a course for Harrenhal. After this Norren offers up his chain to lord Manfryd and recommends sending him to King's Landing as a traitor. Instead Manfryd refuses and raises the banner of King Aegon II Targaryen over Maidenpool, claiming that they are all traitors.