Nienna was one of the Queens of Valar, the sister of the Fëanturi, Mandos, and Irmo.
She is acquainted with grief and mourns for every wound that Arda suffered in the marring of Melkor.
The Silmarillion
It was told that she brought strength to the spirit and turned sorrow into wisdom. That’s why she was known as The Compassionate.
Olorin / Gandalf learned much from her.
