The reader has to believe that your characters exist or could exist — and they need to be distinctively drawn. And nothing better defines characters than their actions, their purpose in life. Their purpose may be good or evil. It doesn’t matter. All that matters is that the reader sees their actions and purpose, believes them, and is continuously interested in them.
     Do not write a story peopled with a cast of thousands. Write a tale about one, two or three memorable characters, all of them filled with purpose.