mythical

1. Of or existing in myth: the mythical unicorn.
2. Imaginary; fictitious.
3. often mythic Of, relating to, or having the nature of a myth: a novel of profound, almost mythic consequence.

adjective

Of or existing only in myths: fabulous, legendary, mythic, mythologic, mythological. See real/imaginary.

The adjective has one meaning:

Meaning #1: based on or told of in traditional stories; lacking factual basis or historical validity
  Synonyms: fabulous, mythic, mythologic, mythological