Nephilim

A Nephilim is a child that is born from an angel and human.

They are viewed as an abomination by Angels. According to Metatron, there is only one Nephilim in existence. She passed herself off as a waitress in a restaurant in Ohio. A Nephilim has glowing eyes like an angel, although its glow was somewhat dim, and grayish in color, as opposed to the white or bluish white glow of regular angels. It is unknown if they required vessels like other angels, or if the human body she had has always been hers from her conception.

Ripping its heart out is the first trial to shut the pearly gates of Heaven. As Castiel technically stabbed her, 'ripping the heart out' may only figuratively mean that killing the Nephilim in any way possible will suffice to fulfill the first trial.

Powers and Abilities

 * Supernatural Perception - A Nephilim could perceive the true form of angels.
 * Super strength - They bear enough strength to toss Seraphs around.
 * Enhanced durability - A Nephilim possessed high tolerance for pain and could withstand attacks from a high-ranking angel like the Seraph Castiel.

Weaknesses

 * Angel Blade - the only Nephilim in existence was killed by an Angel blade.
 * More powerful supernatural creatures like Seraphs.
 * Leviathan - Because they can kill angels they can likely kill Nephilim.
 * The Colt - The Colt can kill everythngi exept 5 beings and it is likely Nephilim is not one of them.

Note

 * Although Metatron claimed there is only one Nephilim in existence, it is unknown if there could be more Nephilim in the future.