"Intense" is a good word, yeah... and I enjoy a bit of classical tragedy as well, so, glad we agree on that!
The background is a heavily edited pic I took on one of my walks. When it comes to the sprite, I naturally took some biblical inspiration (fragment from Ezekiel that went "In appearance their form was human, but each of them had four faces and four wings"; Silvercross Society is fixated on fours, for various reasons, so I already knew I'm going to give May four faces (one conveniently on the back, of course). I forgot about the second pair of wings. My bad. Uh... I mean... May has only two wings, since due to her desire to save Cass anyway, she's a bit of an... incomplete angel. Not fully pure, I suppose.
A shibboleth is a phrasing/saying/word that, if said a particular way, weeds out outsiders, in short. In the context of the game, it's the verse from the Covenant of the Shield (one of two holy books of Silvercross Society). May, being an angel, can sense true faith, so she can also sense if the verse is being said correctly (or, with faith). Since Cass couldn't gather enough faith, it outed her as a non-believer.
And thanks! I'm still learning how to make logos by hand, it's pretty fun but gods know it can be infuriating...