General Design
The principle element in the design is the thin straight lines. You can see them frequently from the top to bottom with excellent design. Additionally, the corners are curved so that Mythos becomes so soft and friendly. Therefore, the appearance can be solid and neat but still very ethereal.
The curved corner
However, in the free version, you don't have a static homepage like the demo.
Other elements
The first thing I pay attention to is the color. Besides the background and text color, the sapphire color plays the main role in the beauty of this theme. You can change this color but I still prefer it as it makes me feel extremely peaceful and relaxed.
The default typography is just adequate for a clean and readable blog. Besides, there are many standard fonts for you to choose from.
The white background can be replaced by any color or image. I think that you should add an image to highlight the box-style of the general design.
Custom Background image
On the archive page, there are 3 styles you can select to display post: a list or a grid with two or three columns. Whatever you choose, your page still looks well-organized and tidy without any mistake. Furthermore, the zoom-in effect makes the images so prominent and fancy.
Archive page with 3 columns
The single post page has the featured image as the largest element. It causes a strong impression for readers at first sight. I have no comment about the body part as the texts are well-arranged and easy to read.
Single post page
Mythos even has a 404 error page with a simple design and a unique home page button.
404 page
The footer lies in a different background with a darker color so it becomes distinctive. This background also gives me a sense of elegance and "maturity".
Responsive
When you use this theme in other devices or even zoom in, zoom out the screen, the design still looks good. You can see the example that I took by a free tool here.
The responsive design checked by ami.responsivedesign.is