The Ghost is the ultimate danger in Spelunky. It is not killable, it can not be escaped, and one touch is guaranteed death. Fortunately, it is possible to make it through the entire game without ever seeing it. Unlike many enemies in the game, the Ghost is more of a disincentive than an obstacle. It exists to prevent loitering by greedy treasure hunters, and 'turtling' by the more pusillanimous of defilers.