Diakka, the Poughkeepsie Seer, is a term designating a class of ignorant and evil spirits who are responsible for most of the fraud and trickery which occurs during Spiritualist séances according to Andrew Jackson Davis. Davis theorized that unprincipled and selfish human beings become unprincipled and selfish spirits after their death. These spirits remain close to earth until they surrender their bad habits and elevate to higher levels of beings. To avoid diakka activities, Davis recommended leading a pure, refined, religious life because these spirits are drawn to minds which are most harmonious to their own. A.G.H.
Greer, John Michael. The New Encyclopedia of the Occult. St. Paul, MN, Llewellyn Worldwide. p. 132