Monster

Monster is the collective name given to the children and descendants of Eve. They are supernatural creatures with extraordinary strength and powers, and commonly prey upon humans. When they die, their souls are sent neither to Heaven nor Hell, but to Purgatory.

List of Monsters

Elite monsters

These monsters are of the strongest type, either by being physically stronger than the rest (like with Dragons), or are so unique that it's hard for hunters to hunt.

High-tier Monsters

These monsters are stronger than the majority of monsters, but not among the strongest.

Medium-tier Monsters

These monsters are about average in terms of strength and powers. They are also normally harder to kill than the Lower-tier monsters.

Lower-tier Monsters

These monsters are considered the easiest to kill, and possess the weakest powers. Despite this, they are still dangerous to hunters.

Changeling

Unknown Ranking

These are monsters, who haven't actually appeared (yet), so their placement on this list is unknown.

Banshee (Mentioned by Dean)
Chupacabra (Mentioned by Gordon)
Loch Ness Monster (Mentioned by Bobby)
Lamia (Hunted by Sam and Dean, but never physically appeared in the episode)

Hierarchy

Alphas

See: Alphas

Alphas are the first of each monster, and the direct descendants of Eve. As a result, each one is more powerful than any other member of their species. They are the creators of the rest of their species, and as such are the undisputed leaders of their kind.

Packs

Although many monsters are solitary, some, particularly the intelligent ones, form groups or packs, where they live and hunt together in "nests" or packs. Pack leaders serve as the bosses of these groups. This is not always a definite rule, however, as some monsters known to live in packs, do sometimes live on their own as well.

Monsters known to live in Packs

Known Pack Leaders

Vampire:

Luther - This leader governed a small pack of Vampires.
Boris - This Vampire commanded a hive of Vampires and implemented an important plan.
Lenore
Dixon

Skinwalker:

Unnamed Pack leader - A certain High-tier leader of some Skinwalkers.

Becoming a monster

Monsters are made in a great variety of ways. While this is not a complete list, it show some of the more common methods of monster reproduction.

The most common method, is however simply be sexual reproduction between monsters.

By Biting - Werewolves, Skinwalkers and Jefferson Starships can pass on their curse by biting a human.
By Genetics - Some monsters reproduce genetically without having to turn or infect humans. In some cases their monstrous nature (can) remains dormant for years, making them appear completely human before it emerges. Rugarus, Shapeshifters and Kitsune all reproduce in this way.
By Transfusion - Ingesting Vampire blood turns a human into a Vampire.
By Venom - The Venom of an Arachne can turn its victim into an Arachne.
By Eating Human Flesh - Succumbing to cannibalism for long enough will turn a man into a Wendigo.

Common Attributes

Many monsters share traits and attributes:

Feeding on Humans - Most, if not all, monsters feed on humans - either human flesh, blood, certain organs, souls or all four. Only Shojos, Sirens, and Phoenixes don't seem to eat humans, they just kill them outright. Shapeshifters have never been seen eating people, or having any intent to, however it was implied by the Leviathan Edgar that at least some of them did.
Non-human Eyes - Shapeshifters, Werewolves, Kitsunes, Skinwalkers, Wendigos, Vetalas, Dragons, Rugarus, Djinns, and Rakshasa can all be identified by their strange or unusual eyes, though some require certain conditions to be noticed (such as a Shapeshifter's eyes flashing when seen through a camera).
Claws - Werewolves, Shojos, Kitsune, Skinwalkers (in dog form), Wendigos, Dragons and Lamia, all have razor sharp claws.
Fangs - Vampires, Werewolves, Okami, Jefferson Starships, Wendigos, Skinwalkers, Crocottas, and Vetala posses monstrous fangs. Vampires and Vetala use them to suck the blood of their victims, for others they are used to tear and devour flesh.
Superhuman Strength - All monsters typically possess some degree of superhuman strength, ranging from just stronger than humans, to being able to lift a man with one hand or snap steel chains, with the possible exception of Sirens.
Shapeshifting - A common power of many monsters is the ability to change their form. Some, such as Shapeshifters, Sirens, Rakshasa, and Jefferson Starships, can change into whatever they want, while others are more limited. Dragons, Crocotta, Changelings, Shtriga, Phoenixes, Kitsune, Skinwalkers and Djinns can only change between their true form and a human disguise. Some monsters have certain requirements or limitations to their transformations, such as Werewolves, the only monsters that can't control their ability to transform, or Ghouls, which are able to change into anyone, but only if they eat the person's flesh.

Weaknesses

Although there is no universal weakness that applies to all monsters, many share weaknesses:

Silver - Several monsters are vulnerable to silver, the most well known are: Werewolves, Skinwalkers, Vetala's and Shapeshifters. Silver is also part of the thing needed to kill both Djinns and Lamias. Wraiths are vulnerable to silver, to touch it will burn their skin. Silver is also half of what is needed to kill a Jefferson Starship.
Beheading - Vampires, Ghouls and Arachne can be killed by having their heads removed (as can Shapeshifters). This along with silver, is the other half, of what is needed to kill Jefferson Starships. This might work on most, if not all, monsters.
Fire - Many monsters on supernatural have shown that they are vulnerable to and can be killed by fire. These monster are Wendigos, Lamias (with certain herbs), Changelings, and Rugarus.
Vamp-Tonite - As well as dumbing down humans, a side effect of the Leviathan Corn Syrup additive, is it makes the blood toxic to any non-Leviathan monster (Vampires, Werewolves, Ghouls, Shapeshifters etc) who drink it. This is to wipe out the monsters, so that the Leviathans don't have to compete for food resources.
Mirrors - Changelings, Sirens and Wraiths all have their true forms revealed by mirrors.

Appearances

Season One

Season Two

Everybody Loves a Clown (Rakshasa)
Bloodlust (Vampires)
Nightshifter (Shapeshifter)
Heart (Werewolves)
What Is And What Should Never Be (Djinn)

Season Three

Season Four

Season Five

Supernatural Wiki