Here is a list of mythical creatures beginning with this letter and I am constantly gathering information from each continent and continually updating.
Atomy (English)
The Atomy is one of a race of creatures with origins in Medieval European mythology, legend and folklore. These beings can only be seen as disembodied balls of light by the naked human eye, and are not much more visible to smaller creatures either. They occur around Europe, and live in hollowed-out areas in tall trees. They enjoy mischief and practical jokes, and are often too small to be noticed by their victims before the prank is carried out.
Myths and stories about them do not have a single origin, but are rather a collection of folk beliefs from disparate sources. Various folk theories about the origins include casting them as either demoted angels or demons in a Christian tradition, as deities in Pagan belief systems, as spirits of the dead, as prehistoric precursors to humans, or as spirits of nature.