Ghost aren't hard to describe. They're essentially a mix of Blue Öyster Cult and Mercyful Fate, with a dash of Black Sabbath and Pentagram. I even hear some influence from Deep Purple and Uriah Heep with their usage of an organ in a number of the songs. Of course, Ghost is a bit more melodious.
This cut, "Ritual," would be Ghost's single if they had chosen to release one, although I'm not sure it would have flown well inside the mainstream due to the "Satanist" lyrics. Honestly, though, how naive do you have to be to think that they actually believe that?
"Ritual" opens with a lighter guitar riff, which transitions into heavier one, and it works quite well up to the chorus, where the song explodes with big melody. My personal favorite part of the song is the closing section where a nice little guitar solo is played courtesy of...well...I don't know. Remember the guys have chosen to conceal themselves.