Trying to remember the name of D&D-inspired book I read in high school

I’m trying to find the title to a book I read some years ago. I remember that I enjoyed it greatly, but for the life of me, I can’t find it’s name (probably doesn’t help that I read a French translation).

Here’s what I remember:

• I read it in high school, so the book was published before 2003.
• It was part of a pulp series, Forgotten Realms, Dragonlance or something like that.
• It used some of the D&D classifications for dragons. Chromatic dragons are bad and metallic dragons are good.
• The main character was a gold dragon prince or king who had recently come to the position. He could switch between dragon and human form.
• If I remember correctly, the main character had been raised as a human and had only recently learned he could transform.
• He had a one-armed majordomo with wings. A kind of dragon/human hybrid?
• They were fighting against a kind of alien threat. I remember a kind of spiked satellite/planet. Maybe new type of dragons?

That’s all I’ve got. I know this isn’t much to go with, but if it rings any bells to anyone, I’d be really grateful!