Redcaps

Physical appearance
It's unknown what they truly look like, or if they have true forms at all, but they can take on human form. They wear hats dipped in the blood of their victims.

Powers and abilities

 * Super strength - Redcaps are extremely strong, being able to overpower humans with extreme ease. One Redcap easily threw around Dean in a cell and Dean wasn't strong enough to fight back and only survived because Sam used the fairy banishing spell to send the Redcap away.
 * Teleportation - Redcaps can teleport from one place to another in the blink of an eye, and therefore are very hard to catch.
 * Invisibility - All fairies are invisible and can only be seen if they want to or by those who have been to Avalon.

Weaknesses

 * Grained substances - If a grained substance is poured in front of them, they are forced to count each individual grain.
 * Iron - Iron is very harmful to fairies, therefore including Redcaps.
 * Cream - Fairies love cream, and it can be a way to easily appease one.
 * Silver - Dark fairies can be burnt with silver, and Redcaps are murderous, savage creatures, so silver can work on them.