eidolon

noun3

1. •
   A phantom; a ghost or an elusive entity.
2. •
   An unsubstantial image; a spectre; a phantom.
3. •
   An image or representation of an idea; a representation of an ideal form; an apparition of some actual or imaginary entity, or of some aspect of reality.

   • As a species it is extinct; as an eidolon it retains its corporeality – but only if maintained in a state of equipoise. — 1936