As you have noticed, Edith Mythology appears to be a compilation rather than a single work with a single author. In cases like these, the MLA style guide recommends using the title of the compilation as the title of the work and the name of the compiler as the author. Since you were unable to find the name of the compiler, you should leave it out of your citation. Here's an example of how to cite Edith Mythology in MLA format:
In-text citation: ("Title of the Text").
Full reference list entry:
Title of Mythology. Publisher, Date of Publication. Medium of Publication.