When in sight of an intruder, the Gonarch rapidly produces baby Headcrabs in great numbers from its sac, birthing them in pairs. At close range, it uses its front legs to swipe at its foe, dealing massive amounts of damage. From afar, the creature spews out white globs of harmful chemicals from the top of its carapace in a mortar-like fashion, its Headcrab spawn also being immune to the acid. The large pendulous sac that hangs below its thorax is its only weak point. The Gonarch is almost completely invulnerable to damage, being heavily protected by a hard, crab-like outer shell.