The most deadly serpent aboard fictional Pacific Air Flight 121 is the monocled cobra. Like many venomous snakes, the cobra's poison affects its victim's central nervous system. But monocled cobra venom is so powerful that the victim's immune system goes into hyperdrive and actually begins to break down organs and muscles. Death is almost instantaneous.
The monocled cobra is named for the conspicuous design on its hood that can feature either one or two "eyes." The snake can grow up to 6.5 feet (2 meters) long and hunts mostly at night.