Zoostuck 2

my grandfather always said, look in the last place first

Yeah, that would be great advice if you knew where the last place was. Maybe if you had inexplicable time-manipulation powers like everyone else seems to you could, but you just have your fists, your feet, and the ability to make books play theme music of your choice. It's not like you can use any of that to...

Wait a minute. You just had a stupid idea, which might actually work given how stupid the entire universe is. You've got a math textbook right here. If you make it play some dramatic music for a final confrontation, that may make one actually happen.

It's completely stupid, but so is everything else. You give it a shot.

You make the book play a suitable tune and dramatically open the nearest door, which leads to...

In the water closet

A closet filled with water. More water than you've ever seen in your life.

And something's coming out of it... goddamn, it's the arms. Except they're changing into something...

You think your music shenanigans may have accidentally triggered the final battle. What are the arms turning into?