Warhammer 40,000: Tyranids - Hormagaunts

Hormagaunts are swarming shock troops, seeded onto prey worlds in their billions. As simple hunter-slayer organisms, spawned Hormagaunts can be left to rampage across battlefields and populations, wearing down defence lines and forcing the prey to expend lives and ammunition. Many formidable bastions have been buried in literal mountains of these chitinous horrors, driven by the will of a terrible synapse beast.