Consider Phlebas

Bora Horza Gobuchul is a Changer, one of a near-extinct race who alter cell structure to become anyone they want - the most feared and sought-after spies in the universe. Horza fights on the side of the Idirans in a religious crusade against the smug, sterile machine worshippers of the Culture. Now he wants his freedom. But first he must hazard one final mission. He'll engage in a shoot-out in a giant crystal temple. Encounter a grossly obese cannibal determined to eat him alive. And witness a deadly game of Damage on a vast space habitat about to be blown to bits...