So, what is the Shrike anyway? Sorry, we're not going to answer that question here. We're not sure we even can. We do know that this thing—"that ambulatory food processor" (2.168), a "thorn-and-steel Grendel" (3.31), and "a creature which defied physical laws and which communicated only through death" (Prologue.29)—is not something we would want to meet, not in a dark alley, not in the middle of Disney World on the sunniest day of the year, not anywhere, not ever.
Too bad for us, the Shrike makes an appearance in some form or another in every single story, in every single chapter.
In the Priest's Tale, the Shrike appears when Father Duré receives his cruciform. The Shrike takes the form of a hot naked babe in the Soldier's Tale. It is Martin Silenus's muse in the Poet's Tale. Sol Weintraub's dreams of "two ovals of deepest red" (4.299) are clearly the Shrike's haunting blood-red eyes. Brawne Lamia never sees or mentions the Shrike in The Detective's Tale, but she has a lot of doings with the priests of the Shrike Temple. And in the Consul's Tale, it might be the Consul himself who's to blame for releasing the thing, even though he's never had a personal encounter with it.
But as the novel progresses and the pilgrims get closer to the Time Tombs and their final meeting with the Shrike, the Shrike appears less in the story. Could the Shrike be a deadly red herring?
The Shrike definitely has something to do with religion. Everyone who sees the Shrike either considers himself (or herself) religious or is grappling with religion: the two priests, the Islamic soldier, the Jewish scholar, and the poet who was involved in the creation of numerous religions. Unlike most people who have met the Shrike, these people saw him and lived to talk about it. You might even say they were blessed. (It's interesting to note that the two least religious people in the party—Brawne and the Consul—never mention having a personal encounter with the Shrike.)
But you know, if we were them, we wouldn't be complaining. After all, the Shrike, also known as the "Lord of Pain and the Angel of Final Atonement, comes from a place beyond time to announce the end of the human race" (3.389). At least that's what some people believe. Other people believe "that mankind somehow created the thing" (3.393), just like some believe that man created God. And then there's Silenus, who thinks he created it by writing his Cantos, which just might be a poetic Bible of sorts.
One thing is for sure: when the Shrike appears, nothing good ever happens, since he (it?) usually kills someone. Or multiple people. And it's bloody. Really bloody. Johnny Depp getting sucked up by a mattress in Nightmare on Elm Street bloody. If the Shrike is representative of religion, he baptizes people in their own blood.
There's a moment in the book that says a lot about the Shrike, even though the Shrike isn't in it. It isn't anywhere in Merin Aspic's tale. But when he communes with the dolphins on Maui-Covenant, he talks to them. "What do you miss most of Old Earth's oceans?" (6.272), Merin asks the dolphins. "miss Shark/miss Shark/miss Shark/miss Shark/Shark/Shark/Shark" (6.274) they respond.
Okay, so the dolphins aren't that eloquent, but it's crazy to learn that they miss sharks. We played Ecco the Dolphin. We know dolphins and sharks are not BFFs. And it makes us think: if dolphins need sharks, maybe humans need the Shrike.