They bite. And when they do, they venomate whomever or whatever attacks them. Cobra venom has a neurotoxic dominant venom, which shuts down the brain and nervous system, and paralyzes its victim or attacker, eventually stopping the heart (blood flow) and lungs(breathing). Cobras (including the King cobra) have solid fangs, each with a groove along the length of it (to help the venom delivery), as opposed to hollow fangs, like rattlesnakes have. Snakes which have grooved fangs generally inflict multiple bites or hang on and "chew" (actually press or chew) in the venom, to insure good venomation.