At the Queen's Command — Michael A. Stackpole

The colonies of Mistria are in turmoil. They face wars between the competing empires and and insurrection from natives and colonists alike. Prince Vladamier is a Norillian noble, and Nephew to King Richard. He has little political power, but struggles to ensure the colonists interests are represented back in the court. The one thing he does have is a wurm... one of the few existing "dragons" from a clutch of eggs discovered in the old world, hundreds of years ago. As Mistria swirl into chaos, Vlad is married off to an old world princess. This new alliance is supposed to help supply money and mercenaries to put down the various insurrections. But, nobody suspects that Vlad's wurm is about to undergo a change that will impact the worlds delicate political balance...