Howdy! I’ve got another Name That Trauma query.
I’m struggling to remember the title of a Young Adult horror novel, in the vein of Fear Street but not from that series, involving a tentacled monster (which may have lived beneath a high school) that was killing students. I remember only one of the kills specifically, but it stuck in my mind because the monster used its tentacles to pop off the victim’s fingernails “like soda-can tabs.” (may not be an accurate quote, but it was something like that.)
I also remember a killer leaving poems for their victims, including one that ends with the line, “Will they wire your coffin with cable?” This might be from the same novel as the tentacle-monster, or it might be a different one.