I should have killed him when I had the chance.”“You showed mercy, Nina. Never regret that.”But mercy was a luxury Matthias could afford. He was dead, after all. It seems rude to mention that, my love.
-- Nina (The Drowning Man: 3. Nina)

Importance: This quote establishes Nina’s view of the world as well as the effect Matthias’ death has on her psyche. At the beginning of the novel, his voice acts as an extension of her inner thoughts. This is notable because Nina is bitter, violent, and struggles to see the good in people. Matthias’ voice is a reminder of how much Nina is struggling with his death, and it is the only thing that keeps her going. This establishes the beginning of her character growth as she learns to live life without him.

Here, for a short time, the demon that ruled his nights and troubled his dreams retreated, held at bay by...
-- Nikolai (The Drowning Man: 4. Nikolai)