- last post: 01.01.0001 12:00 AM PDT
Covenant bombard a planet with heavy plasma and basically wipe out anything that would make the planet habitable, including burning down forests, burning the water bodies to vapors, things along those lines. As a result, the planet becomes barren, smooth (Glass). I actually thought originally, and still unproven, that the heat caused by the plasma literally forms the surface of the planet into a glossy, hard solid much like glass. Think of volcanoes, when they erupt, they leave Obsidian in their midst.
After a planet is destroyed I believe they just leave it, as seen with Sigma Octanus, if I'm correct.