The reason for the monster is probably the fact that Beastman is playing, but we'd like to think it's more because bass, when used properly, is a monster in itself. That's why we've dubbed this creature the Bassmonster, with large brooding eyes and fangs designed to take a bite out any high-tones that try to sneak into the venue that night.
As far as the design aspect, Alert's flier is a bit more complicated than you might notice on first glance. The hard lines are accented by a folded paper layer underneath, giving it a feeling of more technical prowess than one might notice with a passing glance. It adds to the whole flavor of the thing without ever being distracting.
We're also rather fond of the color choices made here. The blue makes it really pop, but also gives us the feeling the night will be filled with relaxing sounds. That's probably not going to be the case, but the twilight grooves certainly evoke a feeling of complacency. Perhaps if you're the Bassmonster, you enjoy bass rattling you brain around a bit more than most people do.