Gregor and the Code of Claw by Suzanne Collins, now you can read online.
PART 1: The Code
Chapter 1
Gregor's back pressed into the cold stone floor as he stared up at the words on the ceiling. His eyes and skin were still stinging from the volcanic ash that had engulfed him hours ago. Between the burning in his lungs and the rapid beating of his heart, it was hard to get a full breath. To steady himself, he tightened his grip on the hilt of his newly claimed sword.
As soon as he had retrieved the sword from the museum, he had run to this room. Every inch of it — walls, floor, and ceiling — was covered in prophecies about the Underland, this gloomy warring world far beneath New York City, which had consumed Gregor's life for the past year. Bartholomew of Sandwich, the man who had founded the human city of Regalia, had carved the prophecies some four centuries ago. While most of his words were for the benefit of the Regalians, they also made reference to many of the giant creatures who lived in the neighboring lands down here — the bats, the cockroaches, the spiders, the mice, and, most often, the rats. Oh, and Gregor. Several were about Gregor. But they didn't call him by his name. In the prophecies, he was known as "the warrior."
Gregor hadn't allowed anyone to enter the room with him. He'd wanted to be completely alone when he first read this prophecy. Everyone had taken such pains to keep its contents from him in the last few months that he had known it must say something awful. And he had wanted to be able to react to the awfulness without anyone watching him. Cry, if he needed to cry. Scream, if he needed to scream. But it turned out it didn't really matter, because he'd barely reacted at all.
"You've got to face this thing. You've got to understand it," he told himself. So he forced himself to focus on the precisely chiseled letters again.
As he reread the words, it was as if he could actually hear a clock ticking along with the lines. It was, after all, "The Prophecy of Time."
Tick, tick, tick, tick, tick, tick, tick, tick, tick, tick, tick, tick, tick, tick, tick ...
The war has been declared,
Your ally been ensnared.
It is now or it is never.
Break the code or die forever.
Time is running out Running out
Running out.
To the warrior give my blade. by his hand your fate is made.
But do not forget the ticking
Or the clicking, clicking, clicking.
While a rat's tongue may be flicking,
With its feet it does the tricking.
For the raw and not the jaw
Makes the Code of Claw.
Time is standing still Standing still Standing still.
Since the princess is the key to unlock the treachery,
She cannot avoid the matching
Or the scratching, scratching, scratching.
When a secret plot is hatching,
In the naming is the catching.
WHAT SHE SAW, it is the flaw
Of the Code of Claw.
Time is turning back