Shadow & Claw by Gene Wolfe

"Shadow & Claw" is a science fiction novel set in a distant future where the Earth's sun is dying out. The protagonist is a highly skilled torturer belonging to a guild, who is exiled for showing mercy to a prisoner. The narrative follows his journey through a world filled with strange creatures, ancient technologies, and complex political machinations. The protagonist, armed with a sword that can cut through any material, must navigate this world, dealing with love, loss, and betrayal, while also questioning the nature of his own reality. The 5111th greatest book of all time