2000s Young adult book about a community that lived underground and another that lived in the city above; some people became dragons when they dreamed

Question

I'm looking for a book I used to love when I was a teenager for my cousin. I think it would be in the 2000s now in the UK.

It was about this community that lived underground and another that lived in the city above. A young boy wanted to come to the surface as he dreamed of dragons and there was a girl in the castle above whose mother was of status.

When they both dreamed they turned into dragons. There was another boy who pretended to be a servant who was actually the "bad guy" who also became a dragon when he dreamed and they ended up fighting as dragons and killed him. I think one of the underground characters was called Scrub?

Answer 1

The book is called Basilisk (2004) by N.M. Browne.

This evocative story of greed, power, and deception sweeps from the underground cave network of the Combers, living like spiders among the endless tunnels and ropes, to the beautiful city inhabited by Abovers. When a young man named Rej discovers the body of a murdered Abover in the combes, their worlds begin to draw closer. He swears vengeance for the murdered man and takes a great risk in going above. There he is placed in the care of Donna, a beautiful young woman trapped in her life as a worker. Food and clothing are rationed, while slaves and workers are forced to live in meager barracks. But Rej and Donna have more in common than a miserable existence; they have weirdly identical dreams of dragons flying in a clear blue sky. They are even more surprised to learn that the city's cruel leader, the Arkel, is determined to find a way to bring just such dreams to life in order to literally scare the population to death. The connection Rej and Donna make leads them on a dramatic adventure to save their loved ones from the Arkel's terrifying plans. N. M. Browne has created an unforgettable world in this richly layered narrative.