story identification - Science-fiction book where the protagonist has a hidden blade inside his body

I'm searching for a book I read 10 years ago, from which I remember only a few details:

• In the distant future, the central planets of the galaxy are ruled by a king.


• The main protagonist is an acquaintance of or becomes friends by the end of the book with the ruling prince.


• At some point the main protagonist gets imprisoned/enslaved on an amusement park planet.


• He has a blade/knife which can cut through anything that wasmade from a strange meteor.


• In order to hide the blade he has a sheath inside his body's skin (he can get the blade out by contracting muscles in a special way).

By using the concealed blade he escapes from the amusement park planet (together with a woman he had met there) and, later, meets the prince, who travels in disguise.

The book had a short name, similar to "Orion", "Andromeda" or some other celestial body.

Answer

This is reminiscent of the Sten Chronicles by Chris Bunch and Allan Cole.

A series of 8 novels published from 1982 - 1993.

In the first novel Sten the eponymous hero does indeed have a knife inserted into his arm...

It was possibly the deadliest fighting blade that had ever been constructed. The crystal tapered to a hair-edge barely 15 molecules wide, and the weight of the blade alone was enough pressure to cut a diamond in half. Sten tucked the knife in an unused suit storage pocket. He already had the sheath built. Hite had done that for him. He and Sten had hidden out in a normal-environment disused area. He'd put Sten out with a central anesthetic. And then delicately gone to work. The sheath was inside Sten's lower arm. With pirated microsurgery tools, Hite laid back a section of Sten's skin down to the dermis. He put an undercoat of living plaskin next to the subcutaneous tissue, then body-cemented into place the alloy U-curve that Sten had already built. That would keep the knife's blade from touching anything--including the U-curve. A wrist muscle was rerouted across the mouth of the sheath to keep the knife in place. Then Hite replaced the layer of dermis and epidermis over the surgical modifications and body-cemented Sten back together. It took several cycles to heal.

Over the course of the novels Sten becomes the favourite of the Eternal Emperor who was known for travelling the universe in disguise on occasions.