THE RINGS OF TANTALUS

Coronet paperback, 1979. Cover artist uncredited.

"Commander James Conrad and his team of Expendables face the unknown dangers of an alien world in their mission to find planets suitable for colonisation. 

First the Expendables went to Kratos - and faced the Deathworms. Then they went on to Tantalus and tried to fathom the Rings - which could only have been fabricated with the help of highly sophisticated machinery. And then they discovered an alien spaceship orbiting the planet in strict silence and uncommunicability. 

When they finally boarded the vessel, it was obvious that it had been derelict for centuries - as a result of some dreadful battle. Meanwhile down below, the enigmatic Rings lay waiting to deal with intruders - as did the deadly vampire tree..."