The Khan Worm, named by Dean Winchester, is a new type of supernatural creature recently created by Eve, Mother of All. There is no official name for it, as it is new, and humans have not given it a proper name.
At some point, a second form of the Khan worm came into existence, described by Dean as like a "cousin" to the first, this version does not take control of the host body. Instead this version of the worm acts more as a parasite.
The Khan Worm, as the name suggests, is a worm that enters into people's head through their ears or mouth, and controls their actions. Dean says it is like a Khan Worm on steroids, and also refers to it as a "twelve inch long herpe." When possessing people it leaves dark green sludge in it's victims' ears, though it can stop this if it wants. It also spills the same sludge out of its victim's nose when it is injured or in pain.
From its comments, it is likely, that like most monsters, it eats humans.
The second version of the Khan differs from the first in several respects. This variety absorbs all bodily fluids, eventually causing the host to go mad with thirst, drinking any liquids they can find, eventually forcing the host to kill; then in its state of heightened thirst, they will drink the blood from other people. This version of the worm acts more as a parasite, drying out their hosts and moving on. This version appears to have originated in the Middle East, though how long it has existed is unknown. It's also unknown if Eve directly created this version or if it naturally evolved (presumably from the first).
Unlike the first which goes into people's heads, this version enters the stomach, and forcibly introduces itself through its victim's mouth and down their throat.
This creature appears as brown worm, or caterpillar, possessing two large black curved fangs. However, it has the ability to "possess" humans by entering their heads. They also have the ability to pass unnoticed from person to person, so it can kill its host as it pleases.
The second version is smaller than the first, and much sleeker. It is closer to black in color and its fangs are white.
Created by Eve, she planted the only known worm inside a trucker, who goes on to kill his family. It then passes to one of his co-workers who kills 12 people. While investigating the murders, it infects Dean who kills his cousin Gwen Campbell, and then infects Samuel, and finally Bobby who kills Rufus while possessed. While possessing Bobby, it tells Dean and Sam that it was created by Eve, who intends for supernatural beings to take over the world. It is then electrocuted to death by Dean while still inside Bobby, who manages to survive the experience.
Four years later, a variant of the khan worm possesses an American soldier held prisoner in Iraq. When two soldiers try to rescue him, the worm attacks and infects them while its original host is killed. This variant doesn't take complete control of the body but compels the host to drink excessive amounts of liquids to the point that they drink blood or gasoline before the host dries out and the worm moves on to a new host. This catches the attention of Sam, Dean and Cole Trenton who try to save Kit Verson, the worm's surviving host. Kit turns out to have at least three khan worms inside him and infects Cole with one. Sam kills another and the last forces Kit to retreat. Sam captures Kit and tries to save him, but is ultimately forced to kill him and the worm in self-defense. However, Dean is able to force the other worm to leave Cole through extreme dehydration by turning a cabin into a sweat lodge and kills it.
- Possession - Like angels, demons, or ghosts, it can possess humans. While in possession of a host, it can access all of its host's memories. This is its primary ability, as it's true form is extremely weak and delicate. The second variant of the khan worm doesn't possess this power in as strong a version: it doesn't take complete control but instead compels the host to drink excessive amounts of liquids and to attack others so it can move on when the host is too dry for it to survive. A strong-willed host can resist this for at least a time.
- Supernatural strength - It is small and weak in its true form, however it is able to magnify the strength of any host it has taken. The second variant also possess this power, but is weaker than the first.
- Supernatural Durability - The worm enhances the durability of its host, allowing them to survive bullets and withstand considerable damage. The second variant will leave the host if the host is fatally injured rather than remaining however.
- Super agility - When not possessing someone, the worm is incredibly quick and agile, able to jump host to host with startling ease. However, the variant, while still agile, is less so than the original, being able to be easily squashed.
- Crushing - Though agile, the Khan worm is vulnerable to being crushed easily.
- Extreme Dehydration - A variation of the Khan worm that feeds off hydration can be ousted from a body by not consuming any liquids for a prolonged period and being forced near extreme heat sources.
- Electricity - The Khan Worm can be injured by electricity. Prolonged duration exposure can kill it. It is likely that this is its weakness due to it potentially being connected to its host's brain, an organ which runs primarily off of electrical signals. The other variant seems not to have this weakness or is less vulnerable to it as it didn't leave Cole Trenton when he was repeatedly electrocuted for long periods.
- This is the first of two supernatural creatures that Dean has named, the other being Jefferson Starships.
- The name "Khan Worm" is a reference to the movie Star Trek 2: The Wrath of Khan, specifically the scenes involving the parasitic Ceti Eels. Like the Khan Worms, the Ceti Eels are worm-like parasites that burrow their way into the victims' ears and take possession of their minds.
- As one can assume that this was an alpha, the weaknesses and abilities of other Khan Worms - if they existed - may have been slightly different, as alphas are shown to be superior to others of their species (i.e. Alpha Shapeshifter not being vulnerable to silver, Alpha Vampire having extendable fingernails). This may be why the variant species is weaker and different.
- The variant version of the khan worm looked similar to a Goa'uld, a parasitic alien race from the show Stargate SG-1. The worm even changed hosts in the same manner as the Tok'ra variant of that species.