http://www.netrover.com/~timt/cheats/l/leathergoddessesof.html (Amiga Plus Extra No. 5/97, 05/1997)The answer to the Sultan's riddle is "Riddle".
To get past the assassin in space, fight him until he is disarmed. Take his sword and give it back to him. He will then realise that you are a good guy, and that he has no chance of winning. He will then kill himself.