Art: There's not much of it, but it's not ugly or distracting, and that counts for a lot.
Writing: I'll give full marks here because the truly impressive amount of good content outweighs the fact that the writing itself is just okay on a technical and "vibes" level. There's a difficult balancing act to be done between straightforward, clear description and evoking a mood, but I would say this leans a little too much toward the former. I think the quality of the content warrants the occasional flourish in the presentation.
Game Design: Full marks again, in that I could probably dock a star for trying to do way too much for such a small format, except that you pulled it off so well for the most part, you get a bonus star for effort, and it all balances out. You did a great job of having each aspect of the scenario makes sense from both the perspective of what it is technologically and how it's represented in the mythical fiction.
Theme: Six out of five, if that were possible. I still have almost another 30 to read, but if this isn't Best in Show for interpretation of the theme, I can't wait to see what else is out there. You wove the myth into all aspects of the scenario and made it all make sense for Mothership. The only thing I thought I'd find that ended up not being there was some interpretation of the command not to look back while leaving the Underworld. I don't think you necessarily need to do that, just sharing that detail of my experience reading in case it's useful.
Layout: Functional. As with the art, you didn't make the mistake of trying to do too much. I like the idea of making the map just with typography, but that kind of type art requires serious typographical skills to execute well.
Utility: Let's face it, this is a zine-sized adventure in a trifold format, so obviously the Warden needs to either be good at ad-libbing details or do a lot of prep. That said, the story is cool enough that I could see myself making that effort.
Favorability: Will certainly be on my toplist. If you want to sell this, I would strongly suggest finding a good graphic designer and building this out into a zine. Add a bit of the real world outside for intro and outro, give each of the locations a page or two, develop the individual Medusae a bit more... create more explicit sidequests for the Stephanie and Colosseum drachmas, etc. Maybe even some other locations that aren't part of the main plot. I could see this being a bit like Prospero's Dream in that it could be run as this specific scenario but also used as a sandbox setting for other missions.
I've seen a number of pamphlets that were long on visual design and short on story... I don't know whether any of those people have the time to take on a big project (or if you do), but it would be cool to see a collab.