Gourgeist can come in four different sizes, and these differences are echoed in their speed and power. Human trainers have assumed these formes to be set the moment the spirits of the dead became Pumpkaboo, and carried with them through evolution; consequently, they have exploited the Gourgeist's ability only by catching their favored type to begin with. Wild Gourgeist, however, are capable of shifting their sizes through the consumption of large quantities of money and jewels which are rarely found outside human possession, and are capable of storing other items within their eyes to be used at their convenience.
It is widely believed in Kalos that all who listen to a Gourgeist's song will be cursed with ill fortune only for the duration of the next month, but that the consequences of the month's luck can last for the rest of one's life. There is no truth to this rumor, and the many anecdotes which support it are nothing more than the product of confirmation bias and self-fulfilling prophecy; the tale's origin can be traced to a remarkably successful scheme by the Gourgeist themselves, which only a few of the most skeptical academics have managed to uncover.
A Gourgeist's song is nothing more than the ruse of a common pickpocket, for although Gourgeist seek many items, they can rarely triumph over the elite pokemon trainers who hold so much of Kalos' wealth today in honest combat, nor did they have any more hope of defeating the nobles who could claim both human and pokemon bodyguards, along with their own weapons, in times of old. That this scheme has prevailed for so long might be thought a testament to human gullibility and superstition, but it is hard to fear pickpocketing from a creature whose very arms are typically mistaken for hair!