I had a copy of Hyperion but didn't read it for years because the scary knife robot on the cover seemed intimidating. I finally read it, and all the sequels, and they were great books, and hell YEAH that was an intimidating knife robot! Sometimes you CAN tell a book by its cover.
I find it awesome that the true nature and mission of the Shrike remains a secret.
The scary knife robot is way, way more intimidating in person.
I didn't know there was a type of bird called a shrike until long after I read Hyperion. The birds look and sound like cute little songbirds, kind of like a smaller mockingbird. But the way they hunt is hardcore. They capture small prey (lizards, grasshoppers, etc) and impale them on a spike from cactus or a broken branch. Then they return to eat them at their leisure.
It's rare to see their caches but a few times I've been out hiking in the desert and seen the remains of a little critter on a cactus thorn.