iamthealterego
The mission is this gentleman - sail the ocean, climb the cliff, descend the pipes, swing across the ravine, pass safely though the cave of snakes followed by the cave of rats and then the cave of spiders
There are several things you can cross, lines come to mind at first. To cross the line is to do that which you are advised against. Now while some lines, I won't say most, but some lines are agreed upon by most of the human population, while others are simply put upon you by a select few others.