Praxis is a Klingon moon orbiting Qo'noS. It was their key energy-production facility until a major mishap, attributed to poor mining practices caused an explosion that disintegrated most of the moon itself in 2293. A subspace shock wave from the incident disrupted operations aboard many starships, including a Starfleet ship, the Excelsior. The result of that explosion polluted the ozone layer of Qo'nos, leaving it with approximately 50 Earth standard years of life left. This lead to peace negotiations with the Federation, a key precursor to a Federation/Klingon alliance being secured.
Appearances/References
Background
It is scientifically unclear what kind of explosion would cause a shock wave that spreads in only a two-dimensional axis at faster than light speeds, but it is clear the Klingon miners were using future science inappropriately if they vaporized half of a moon-sized world.