The original worm was actually held in a jar by oryx's father. Before he died he would talk to it. The worm started to talk to oryx as well. That's when they found the ship, the needle and dove into the center and found the leviathan. The leviathan told them that they were nothing but the bottom of the food chain. They reject this notion and the worm tempts them with sybiosis. (I'm not trying to be a jerk, just really liked the book of sorrows)