Reapers

Reapers are servants of Death. They assist in maintaining the Natural Order, and are completely neutral, not aligned with Heaven or Hell nor Purgatory. According to Castiel, Reapers will sometimes appear in mass gatherings in prelude to a great disaster such as the eruption of Mount Vesuvius in Pompeii.

Background
Reapers are first credited in John Winchester's journal. Dean and Sam Winchester first encounter a Reaper in the episode "Faith", seen assisting Roy Legrange "heal" the sick. However, only someone who is dead or near-death (or is the target of it) can see a Reaper. The Reaper can be controlled by Black Magic and was released by smashing the Rosario controlling it, upon which it turned on the person who was controlling it: Roy Legrange's wife.

A different Reaper, Tessa, appears in the season 2 opener "In My Time of Dying". After Dean is left in a near-death coma following a car accident, the Reaper, disguised as a young girl, eventually persuades Dean to come with her. However, John Winchester offered his soul and the Colt to restore his fallen son. The Yellow-Eyed Demon, then taking the offer, possesses Tessa, allowing Dean to live.

Tessa has a second appearance in the fourth-season episode "Death Takes a Holiday", along with another reaper, in which Sam and Dean to try and stop the breaking of a seal, which involves two reapers being killed.

Reapers make a fourth appearance in the fifth-season episode, "Abandon All Hope...". dozens appear in a deserted street through Castiel's eyes. Bobby later reveals that they are in the town because Lucifer is planning a ritual to raise their "Boss", Death, one of the four horsemen.

Reapers make a 5th appearance in the fifth-season episode, "Two Minutes to Midnight". They appear through Crowley's eyes, standing outside of a building where Death supposedly is.

Tessa makes an appearance in the 6th-season episode, "Appointment In Samarra" along with the Horseman Death. This marks the 6th appearance of reapers on the show.

Reapers make a 7th appearance in "Death's Door" when a reaper comes after Bobby in his coma when he is shot by Richard Roman.

Powers and Abilities

 * Invisibility - Reapers are naturally invisible to the naked-eye, unless they're dealing with the deceased, or if they chose otherwise. Angels like Castiel are capable of bypassing this skill and see reapers with clarity.
 * Teleportation - Reapers can appear anywhere on the face of the Earth, including in human minds.
 * Resurrection - Reapers are capable of reviving the dead, though most don't.
 * Terrakinesis - Reapers can shake rooms by their presence.
 * Time manipulation - Reapers are able to stop time, causing objects that measure time to permanently break.
 * Astral projection - Reapers can project their astral form, similar to the angels.
 * Superhuman Stamina - Reapers do not grow tired, and will never leave their victims, unless a supernatural event disturbs them.
 * Invulnerability - The only known way to kill a Reaper is with the scythe of Death and a special incantation.
 * Killing Touch - Reapers can kill any being by touching them, except stronger beings. The beings obviously immune are God, the Four Horsemen and the Archangels.
 * Telekinesis - Demonstrated when Tessa pushed Dean.
 * Immortality - Reapers are not subjected to hunger, disease, or time.
 * Flight/Levitation - In their true form, they have the ability to fly and/or levitate.
 * Perception Altering- By this ability, Reapers is able to change their appearance so instead of appearing before spirits in there true, more frightening form, this allows reapers to make people see what they want them to see.
 * Healing - Reapers can use their powers to heal disease and injuries, however they have to give the injury or disease to someone else if it's life threatening.
 * Memory Manipulation - Reapers can make mortals forget things and can also restore memories.
 * Intangibility - In their true form, they are like ghosts, and can phase through solid matter without any kind of injuries.
 * Electromagnetic Interference - The appearance of a Reaper can cause lights in a room to flicker.

Weaknesses
Despite being quite powerful beings, Reapers do posses a few weaknesses. As their master, they are completely under Death's control, as Tessa puts it "He calls us, we don't call him" as such Death is the only known being who can stop Reapers permanently. Powerful Demons like Azazel and Alastair can overpower Reapers, and in Azazel's case, even possess them.

Reapers can also be imprisoned, and warded off by spells (Enochian runes or symbols), however nothing other than Death can permanently stop them, as such these will only temporarily hold them. Certain spells can also bind them. Also like most beings, they are vulnerable to Death's Scythe.

Season 1

 * "Faith"

Season 2

 * "In My Time of Dying"

Season 4

 * "Death Takes a Holiday"

Season 5

 * "Abandon All Hope..."
 * "Two Minutes to Midnight"

Season 6

 * "Appointment In Samarra"

Season 7

 * "Death's Door"