User blog comment:B214/Question and Answers 6/@comment-201.215.165.7-20161220161455/@comment-10330822-20161220214558

Well, first off, Judaism, Christianity, and Islam are all worshiping the same god, the God of the Bible. So "Allah" is dead in this story. The difference between these religions is that they follow different prophets, but they are all worshiping the same thing, the God of the Bible. For example, Islam follows Mohammad's teaching on God and believe Jesus was just a prophet, not the son of God. Judaism is the same situation, Jesus was just a prophet, not the actual Messiah, or son of God.

But the thing is. The reason True Longinus is so powerful and so well revered is because it killed Jesus, the son of God. In other words, this series insinuates that Judaism and Islam are wrong and Christianity is right. Jesus was, in fact, the son of God.

So, at least to me, it doesn't make much sense to include Islam in the story because it doesn't really have anything to add, just like how Judaism isn't talked about.