" Hades allowed himself the faintest smile, but there was nothing cruel in his eyes.
‘I can entertain the possibility that you acted for multiple reasons. My point is this: you and I rose to the aid of Olympus because you convinced me to let go of my anger. I would encourage you to do likewise. My children are so rarely happy. I … I would like to see you be an exception.’
Nico stared at his father. He didn’t know what to do with that statement. He could accept many unreal things – hordes of ghosts, magical labyrinths, travel through shadows, chapels made of bones. But tender words from the Lord of the Underworld?
No. That made no sense. "

― Rick Riordan , The Blood of Olympus (The Heroes of Olympus, #5)