Who is Jesus Christ from Johnny Got His Gun and what is their importance?

After being drugged to stop his head tapping, Joe Bonham sees Christ approaching the train station like a purple-cloaked mirage and sitting down, joining a blackjack game. When someone says, "Christ I wish we had a drink here," Christ produces sixteen-year-old whiskey and they drink. He can do anything except hit a twelve. When the train leaves, Christ can go with them only a short way, as he has many trains and dead men to meet. He mounts the locomotive and screams, his robes trailing. Bonham runs toward him, throws himself into the hot sand at his feet, and begins to cry.