I want to completely and utterly destroy a planetary civilization, while leaving technology and infrastructure (on land) more or less intact.
Essentially, some squishy land bound (bipedal, carbon based) aliens earned the ire of the energy eating rock aliens who have decided to forcibly remove them and take their metals.
By working together the rock aliens can harness and direct ~0.00000001% of the star's output (there are only a few thousand of them) and can use their psychic powers to reflect and bend light. They can also work together to accelerate large rocky/metallic masses (like asteroids). They cannot grip or directly move gasses or liquids.
The rock aliens love metals, especially metals with a high melting point and/or high thermal conductivity. They want to remove all the squishy life forms and atmosphere from the planet's surface so they can take away all the metal on the surface without interference. The squishy aliens have many high profile metal buildings on the surface but also have an annoying tenancy of using particle weapons and mass drivers to inconvenience or destroy the rock aliens.
The rock aliens don't want to bombard the planet with asteroids because that would bury all the useful metal (it is also bad for rest of the story), and the atmosphere is inconvenient to them because it transfers heat (they prefer vacuum for because it doesn't absorb energy as well).
How can the psychic rock aliens remove the atmosphere (and optionally the ocean) in a short period of time (less than ~800 years) with the minimum use of energy and least damage to infrastructure on the surface.