Rakshasa

"Rakshasa. It's a race of ancient Hindu creatures. They appear in human form, they feed on human flesh, they can make themselves invisible, and they cannot enter a home without first being invited to. They dress up like clowns, and children invite them in. Why don't they just feed on the kids? Not enough meat on the bones, maybe? Apparently, Rakshasa live in squalor. They sleep on a bed of dead insects. And they have to feed a few times every 20 to 30 years -- slow metabolism, I guess. "

The Rakshasa is a mischievous and homicidal imp appearing in "Everybody Loves a Clown".

Characteristics
Rakshasas are creatures from Hindu mythology and are very nasty. They eat human flesh, sleep on a bed of dead insects and are great at shapeshifting. A rakshasa cannot enter a house without first being invited. The one in Supernatural appeared as a clown at the fair who would follow children home, get the child to let them into the house and then eat the parents.

Powers and Abilities

 * Shapeshifting - They can take any form they want.
 * Invisibility - They can easily become invisible.
 * Invulnerability - They can only be killed by brass.
 * Super strength - They are incredibly strong, able to easily over power humans.
 * Super senses - They possess incredible hearing, one was able to over hear Dean's entire conversation, despite being outside the range of human hearing distance.
 * Super speed - They run really fast.

Vulnerabilities

 * Brass - a Rakshasa can be killed with a brass knife. Sam killed the rakshasa in the fun house by breaking off a brass organ pipe and stabbing it with it.
 * Invitation - a Rakshasa cannot enter a home without being invited in. The Rakshasa in "Everybody Loves a Clown" combated this by dressing as a clown so that the children would invite it in.
 * The Colt - Since this gun can kill almost anything, it can possible kill Rakshasa.

Season 2
The Rakshasa is disguised as the blind knife thrower who works with the circus. It appears to children as a clown, and, when they invite it into their home, it kills their parents. Ellen tells them the creature can be killed with a knife of pure brass. As it pursues them, it becomes invisible, but Sam manages to kill the Rakshasa with a brass pipe from the organ in the fun house.