Expendables: The Rings of Tantalus

First they 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 discover an alien spaceship orbiting the planet in strict silence and incommunicability.
When they finally boarded the vessel, it was obvious that it had been derelict for centuries - a...