Madeline Miller said this quote

There is no law that gods must be fair, Achilles,” Chiron said. “And perhaps it is the greater grief, after all, to be left on earth when another is gone. Do you think?”“Perhaps,” Achilles admitted.I listened and did not speak. Achilles’ eyes were bright in the firelight, his face drawn sharply by the flickering shadows. I would know it in dark or disguise, I told myself. I would know it even in madness.