I'm trying to remember then name of an old book I read as a kid, hope someone can help locate it?
Ok the book I read was part two of a trilogy from around the 70s maybe 80s, it starred a hero who was modified by some kind of either advanced tech or alien tech so that he could grow his fingernails and canine teeth when he needed to fight. I think his teeth were poisonous too, and I think he wore a ring that triggered this change somehow. The book was set on some alien planet with spaceships and so on, there was a part where an alien spaceship was found buried underground and the hero went to investigate it, I think there was some link to his power to transform found in this ship.
The cover of the book showed the hero piloting a spaceship with his teeth and "claws" extended and the ring on show on his finger. He wore a seventies looking sci fi helmet.
Um.. Honestly that's about all I can remember of it.. A bit vague I know.. Can anyone help? Does it sound familiar?