Nephilim

A Nephilim is a hybrid creature conceived by an Angel and a Human. The offspring contains a mixture of human soul and angelic grace as a source of power, inherited from both parents. Whenever a Nephilim grew into their power, entire worlds died. As a result, conceiving a Nephilim is strictly forbidden by laws of Heaven and the punishment is death for the celestial parent along with the child.

History
As stated, Nephilim are the result of sexual reproduction between a human and an angel occupying a vessel. Nephilim have glowing eyes like an angel, although their glow is somewhat dim and grayish in color as opposed to the bright white or bluish-white glow of regular angels. A Nephilim's eye color is also related to the angel who sired them; whereas Lucifer's eyes were red, his Nephilim child's eyes were golden. Where Remiel's eyes are golden, Remi's eyes are a dimish golden.

Nephilim were stated to have been quite destructive with their powers, as Castiel and Mirabel from over a hundred years ago stated that whenever Nephilim grew into their full power, entire worlds died, causing them to be forbidden by the oldest laws of Heaven. As a result, they are considered as unholy beings and abominations. A mother pregnant with a Nephilim can ignite a bible upon physical contact. Dagon revealed to the mother of Lucifer's Nephilim child that carrying a Nephilim is always fatal to the human mother. Remiel possessing Karen Singer when she gave birth to Remi, she was able to survive the birth.

Theoretically, removing a Nephilim's grace will turn them into a normal human as removing the grace of an angel would turn them, effectively, human. It is unknown if the procedure is effective. Though Jack had his Grace extracted and absorbed by Lucifer, despite being powerless afterwards, Castiel revealed that his Grace would recharge in time, throwing whether or not they become human into question.

It's later revealed that the Nephilim's grace is what holds their human and angel halves in balance and, when they lose it, their two halves come in conflict with each other, causing the Nephilim's body to shut down progressively. The only way to revert that is for the Nephilim to recharge their grace.

While their grace is an angel's source of power, a Nephilim has their parents Grace mixed with a human soul causing them to be superior to angels In terms of power. When fighting Jane, the angels Metatron and Castiel were easily overpowered and thrown around by her, only winning when Castiel caught her by surprise from behind with an angel blade. The Nephilim lore states, as revealed by Sam Winchester that a Nephilim will eventually become more powerful than the angel that sired them.

Due to their human souls, Nephilim, at least when their Grace has been removed, can go to a human afterlife such as Heaven or Hell though the Shadow believes that they belong in the Empty due to their half-angel heritage. As seen in the case of Jack, in Heaven they are able to sense the true nature of the realm around them and can leave their own personal Heavens and travel to other Heavens that they choose.

Physical Appearance
They have various eye and hair color Nephilims generally appear as attractive humans. Some may posses uniquely colored eyes or hair. They all posses a pair of wings that are spiritual in nature but can be summoned into the physical world.

Eyes
Most Nephilim have the same variety colored eyes a human would posses. But when they us their powers, they have unique colored eyes like purple, violet, silver or have a deeper coloring then regular people depending on their Angelic parents eye color. Like many supernatural creatures when they get emotional or use their powers their eyes will glow a brighter color.

Wings
The wings of an Nephilim are spiritual in nature. When not in use they are invisible and intangible and can only be seen with electronic devices or by those with enhanced eyesight or if they make them visible to be seen by others. They can use their wings to hover or levitate or fly.

Powers, Skills, and Abilities

 * Astral Perception - Remi can perceive the true form of angels, such as perceiving their halos. Such as when Remi could tell that Gabriel wasn't a trickster
 * Super Strength - Their angelic ancestry endows Nephilim with enhanced strength sufficient to overpower and even toss common angels around.
 * Healing - Remi healed being shot several times and stab even cutting her arms multiple times with all different kinds of knifes
 * Resurrection - Jack was able to resurrect his mother at the same time he healed her. However, Miriam indicated that Jack could not resurrect an angel that was "all the way dead" despite his vast power.
 * Telekinesis - Remi threw Spencer, Chase and Kyle against the wall after they shot her.
 * Immunity - Remi is immune to the angel banishing sigil. Also shows an immune to angel warding.
 * Invulnerability - Remi was stabbed by an angel blade and an archangel blade.
 * Regeneration - When the blades were removed, the wound healed in seconds.
 * Super Senses - Remi was able to hear a conversation on a different floor of a building.
 * Teleportation - When Jack grew upset, he was able to teleport away.
 * Telepathy - Jack was able to telepathically call out to Castiel in The Empty, awakening him from his slumber. By touching a person's head, Jack was able to connect with their minds, causing their eyes to glow as well as the veins on their faces. Doing this, Jack was capable of sharing images with the person and seeing what a dreamwalker was experiencing through their powers.
 * Mind Control - She controlled Terrance and Amy forcing them to leave after altering their memories
 * Precognition - Jack had a premonition of Castiel's later confrontation with Dagon which he was able to share with his mother.
 * Sedation - Remi can put people to sleep by touching their foreheads
 * Illusion - Jack was able to alter the images of his shadow puppets to entertain young children.
 * Smiting - Remi possesses the ability to kill or exorcise a demon simply by touching his palm to the forehead of its host. He is able to kill lower-level demons and other beings like monsters with a simple touch. When this happens, a strong white light appears from the eyes and mouth of the victim and burns them from the inside out.
 * Localization - Remi is able to track and locate beings, although not if they are warded by Enochian sigils. She can track warded person's location if they pray to her such as the year Dean was with Lisa, Remi could hear everything he would pray about her even though he didn't know.
 * Pyrokinesis - Remi can burn through ropes binding her.
 * Astral Perception/Senses - Can see things hidden to humans. Vision and hearing at extreme superhuman levels; able to see a symbol on a person's heart that was so small Sam needed a microscopic lens to see it.
 * Lie Detection - Remi was able to tell when the Winchesters were lying to her.
 * Life Force Draining - On the request of Castiel, Jack was able to drain most of his life force, storing it in a flask, so that Castiel could enter the Empty and speak to Ruby.

Harming, Misleading, and Trapping

 * Archangel Blades - Lucifer was able to use the blade on Jack when extracting his power from him. The blade most likely worked on Jack due to his archangel heritage. As a result, Jack's powers were depleted and would recharge at a slow rate.
 * Grace Extraction -  Removing a Nephilim's angelic grace could possibly turn them effectively fully human and render the Nephilim virtually powerless. Lucifer was able to extract some of Jack's grace and leave him powerless. Extracting a Nephilim's grace also renders their bodies unstable, as their human half and angel half will start to attack their cells, which will cause them to die unless their grace is restored.
 * Angel Radio - Hearing "angel radio" caused Remi debilitating pain.
 * Unexpected Mechanical Trauma - While Jack has the superhuman endurance to shrug off bullets and knife wounds, Jack can be knocked unconscious or temporarily stunned with pain by physical forces when he is caught off guard. Sam had once knocked Jack unconscious by electrocuting him with a Taser. A shapeshifter was able to knock Jack unconscious by hitting him in the head with a fireplace poker.
 * Very Heavy-Angel Warding - Jack's powers were severely weakened by the powerful warding in Michael's fortress, leaving him vulnerable to the powers of Michael and Zachariah. The warding was so much that when Jack attempted to use even some of his more easily controlled powers, he could do nothing. In a spot where the warding was weak, Jack was capable of using a weaker ability to melt metal bars.
 * Resurrecting Angel Ritual - Making the ritual using Jack's blood made him feel great pain.

Banishing or Destroying

 * Angel Blades - Castiel killed one with an angel blade. However, Jack could not be killed or even harmed by an angel blade.
 * God - Last time Nephilim were walking the Earth, God had to intervene in order to remove them. With a snap of his fingers, God was able to smite Jack, killing him. Following Jack's resurrection by Billie, he has to be very careful to not use his powers as he will draw God's attention and God will be able to kill him again if he knows Jack is alive before Jack is strong enough to face him.