Nindrahil has lived through the ages of Middle-Earth. She was a scholar in Gondolin before the ruin of Beleriand after which she travelled Middle-Earth to settle in Rivendell. In days past when elves and men were closer she spent a lot of time in the lands between Ered Luin and Rivendell as a scholar and librarian for the Rulers of Arnor. 

After "the Big Split" in TA 861 Nindrahil went back to Rivendell. She started writing her account of the history of Arnor and as this task grew in complexity she formed a group which she called "The Custodians of Arnor". The Custodians all worked together to record the history of Arnor and the lands that formed Arnor before and after its fall. 

As the elves started leaving Middle-Earth in great numbers to return to Valinor The Custodians of Arnor decided to work closer with the race of humans to prepare them for taking over Middle-Earth. Humans were accepted into the Custodians and with agreement from the members of the Custodians of Arnor the group relocated from Rivendell to Bree in an attempt to be in the heart of Arnor and become more active in traveling and recording current events, not just events from centuries ago.

Nindrahil is the leader of the Custodians of Arnor and she resides mostly in the kin house, although she is still seen traveling the lengths of Arnor speaking to people of all sorts, listening to their stories, forever recording notes in one of her diaries.