Vampyroteuthis infernalis, literally translated as 'vampire squid from hell', is a deep-sea cephalopod that may look scary, but doesn't quite live up to its name.
Neither a squid nor octopus, the species has traits of both, but is actually the only known, currently-living, species of the order Vampyromorphida. It's body is generally shaped like an octopus' and it has eight primary tentacles, but it has two wing-like fins on its back, its tentacles are joined together by web of skin, and it has two other smaller, retractable tentacles that are concealed within flaps of that web.
The species' dark-red colour, red eyes, and cape-like webbing are what prompted German marine biologist Carl Chun to give it its rather ominous name. Adding to its vampiric visage are rows of fang-like spines on the underside of its tentacles. These spines, called cirri, are harmless, but by using a 'pineapple posture' of curling its tentacles back around its body, the spines can still dissuade a predator from attacking it. Its reputation is helped by the fact that it lives about 600-900 metres below the ocean surface within a layer called the 'oxygen minimum zone' (OMZ). Oxygen levels in the OMZ are too low for most higher forms of life, but the vampire squid manages just fine, possibly leaving one with the impression that it is the Un-dead.
However, that's about where the scariness stops. Although rather famously attributed with a 'face-sucking blood funnel' in a 2010 Rolling Stone article, research has shown that this creature does not hunt prey, as was previously thought, but instead survives on an omnivorous diet, snagging pretty much any kind of cast-off organic matter they can. It is speculated that this lackadaisical approach to life is what allows the squid to survive in its low-oxygen habitat.