This is the 14725th most frequent Russian word.
печалью
"Печалью" means "with sadness" or "by sorrow" in English.
The word 'печалью' is used in the instrumental case, denoting the cause or accompanying state of the subject's eyes.
Её глаза наполнились печалью, когда она услышала новости.
Her eyes filled with sorrow when she heard the news.
Here, 'печалью' is used in the instrumental case to describe the emotional quality associated with 'звучала' (sounded).
Скрипка звучала с глубокой печалью, трогая сердца слушателей.
The violin sounded with deep sorrow, touching the listeners' hearts.
In this sentence, 'печалью' refers to the abstract state or mood surrounding the individual, again utilizing the instrumental case to indicate this condition.