The enemy forces rolled in overwhelmingly, as if blotting out the very sky.
Tips
history
From 《水浒传》 Chapter 83, describing Liao troops advancing 'pitch-black, blotting out the sky and sun, all bearing black-eagle banners.' Used ever since for vast numbers or scale - armies, swarms, dense foliage, clouds.
usage
Very visual - use when the sheer quantity or size of something literally or figuratively blocks the view. Pairs naturally with 铺天盖地 (spread across sky and earth).
