Marvel Comics has their own horror team of dark and frightening anti-heroes known as the Legion of Monsters. As a result, they are by far the spookiest team in the Marvel Universe, and are definitely a force that no villain would want to encounter alone in the dark. But who are the Legion of Monsters, and what makes them so terrifying?
The Marvel Universe has actually seen a few iterations of the Legion of Monsters, each of them featuring different leaders and new additions to the team. However, there is some overlap of members. The first Legion debuted in Marvel Comics in 1973 from Bill Mantlo and Frank Robbins. That first group was rather short lived, but featured Ghost Rider, Morbius the Living Vampire, Man-Thing, and Werewolf by Night, each of them carrying terrifying powers and appearances to make common folk tremble. They were all thrust together quite by accident with the arrival of an alien known as the Starseed, which was altruistic in nature but was destroyed by the Legion's monstrous tendencies. Morbius and Werewolf by Night couldn't help but attack it, desiring to eat it. While the Starseed tried to heal and restore their humanity, it failed to do so and it died.
After this first team (if you could call it that), other versions would emerge throughout the history of the Marvel Universe, with most of them featuring Morbius and Werewolf by Night as consistent members. In 2007, the Legion had a series of one-shots that featured the same roster of heroes as the first, aside from Ghost Rider who was replaced by Satana Helstrom, the human/demon hybrid. However, the most recent and notable team - the defenders of a subterranean Monster Metropolis - featured Morbius, Werewolf by Night, Man-Thing, the Living Mummy, and Manphibian. The Punisher even joined them for a time when Morbius pieced his body parts back together after he was cut to pieces by Wolverine's son, turning him into Franken-Castle.
From 2008-2012, the Legion of Monsters worked together to protect other monsters from threats such as Hunter of Monster Special Force, a hunter from Japan who had sworn to kill any and all monsters he could find. As a way to protect themselves from the world, the Legion built the Monster Metropolis in the old Morlock Tunnels, allowing them a modicum of safety from the outside world. However, the Legion did recruit the monster hunter Elsa Bloodstone to investigate a virus that was only affecting monsters in a Legion of Monsters limited series from writer Dennis Hopeless with art by Juan Doe.
While the Legion of Monsters does not currently have a series, they're an ongoing team who have had encounters with the likes of Daredevil and even the Red Hulk when he was haunted by ghosts. The Legion of Monsters like to keep to themselves while helping their fellow monsters who have likewise been cast out from normal society, inviting them into their Monster Metropolis below. While there's plenty of threats for the Legion of Monsters to face, the fact that they are still monsters at the end of the day should not be discounted. Many of them have truly monstrous natures that they sometimes can't restrain, often leading to some gruesome and horrific results. The Legion of Monsters are many things, but as their name suggests, they are not human.