Rachel

Rachel was an angel. She was Castiel's lieutenant in the war to win control of Heaven against Raphael, who referred to herself as Castiel's friend.

Powers and Abilities
Although very few of her powers have been shown, Rachel was a common/average angel and had the usual powers.
 * Super Strength - It is unknown how strong Rachel was exactly, but she could have had the strength of a common/average angel and she was strong enough to fight and even stab her friend Castiel, a Seraph.
 * Possession - Rachael requires a vessel while on Earth, but she needs the vessel's consent.
 * Teleportation - Rachel can efficiently teleport anywhere that is not sigil mark protected.

Season 6
In Frontierland, Sam and Dean call for Castiel but Rachel instead answers the call. Rachel says that Castiel is busy with the war in heaven. She yells at the boys for always calling Castiel even though he is in the middle of a civil war. She continues on how insignificant they are and how Castiel is an angel. Dean and Rachel keep arguing until Castiel appears and tells Rachel that he will handle this. She leaves them to their business. Later Rachel summons Castiel to a warehouse. She tells Castiel she is hearing rumors of side deals that Castiel could be possibly making. She demands to know if the rumours about "his dirty little secret" are true. Castiel answers and says "I have to defeat Raphael" and that he has no choice. Rachel then attacks him and the two get into a fight and Castiel kills Rachel. She does though manage to wound Castiel, which weakened him.

She later seen in The Man Who Would Be King, appearing in one of Castiel's flashbacks, as he recounts his return to Heaven after helping the Winchesters defeat Lucifer and Michael. She and a group of other angels show their astonishment at his arrival, and he tries to explain to them the concept of free will, but they do not know what to do with this free will.