Samandriel

"You know that there are some in Heaven that believe despite his mistakes, that Castiel's heart was always in the right place."

- Samandriel

Samandriel - nicknamed "Alfie" by Dean - is an angel who apparently knew Castiel, and admired him for his heart.

What's Up, Tiger Mommy?
He manifests in a vessel somewhere around the time appears where one of the Words of God is being auctioned. Before the auction, he approached Dean and asked him what had happened to Castiel. Dean, however, was unable to give him a straight answer.

During the auction, he bid against Crowley for the tablet. Alfie's offers included the Mona Lisa and Vatican City. Crowley's counteroffers include the "real" Mona Lisa (in which Crowley claims she's topless), Alaska, and the moon. When Mrs. Tran offered her soul in exchange for the tablet and her son, Alfie was impressed and deeply moved by her courage. After the auction was over, he offered her Heaven's protection for her son. Mrs. Tran declined, however, pointing out that the last time angels tried to protect Kevin, they were killed and Kevin went missing for a year.

A Little Slice of Kevin
He was captured by Crowley, who tortures him for information on the succeeding prophets. The King of Hell used an angel blade to inflict damage on Samandriel, who eventually gave up the identity of several next-in-line prophets. When he told Crowley the next generation of prophets isn't born yet, the demon stops the torture, albeit without urgency.

Torn and Frayed
Samandriel was tortured while in custody of demons. His angelic link was disabled by a screw bored into his forehead. When he removed the screw by telekinesis to send a distress signal, his demon captors sought of severing his link more effectively. Naomi then picked up his distress call and sent Castiel to save the captured angel. Castiel in turn also enlisted the help of the Winchesters and Kevin.

Meanwhile, when the demons began to use more screws to disable the angelic link, Samandriel inadverdently began to speak in enochian. This caught the attention of Crowley, who was interested in finding out information from the angels. The angel's agony also caused disturbances in the surrounding area, such as a bush being lit with flames. According to Crowley, the torture has tapped into Samandriel's "operating system" and he has reverted to his "factory settings."

Just before Samandriel was freed by Castiel, Crowley managed to extract information from Samandriel that a tablet on angels also exists. Samandriel didn't want Castiel to bring him to Heaven because the former believed he has betrayed Heaven by revealing secrets that were unknown even to him. He is surprised that Castiel does not know Naomi and realizes that he is being controlled by her. Samandriel indicates that he was once controlled as well. The revelation of what he revealed to Crowley prompted Naomi to order the assassination of Samandriel, to protect the secrets of Heaven and the angels, deeming him a traitor for revealing what any angel would die to protect. Castiel, unable to go against Naomi's orders, stabs Samandriel with an Angel Blade, killing him.

His remains were brought to heaven by Castiel under Naomi's orders, so she could find out how much information Crowley was able to extract. Castiel is left horrified by his death, though Naomi calls him a hero for it. Samandriel's death and Castiel's explanation under Naomi's control, attract the Winchesters' suspicions.

Powers and Abilities
Samandriel has not shown any significant angelic power. He seems to be of the lower angel ranks, as even demons can overpower him. He has shown the following:
 * Angelic Possession - Samandriel needs a human vessel to act on Earth. He also needs the vessel's permission.
 * Eidetic Memory - Samandriel has the names of all the living prophets etched into his memory.
 * Telekinesis - Despite his weakened state, Samandriel was able to push a spike out of his head using only his mind, though it took a lot of effort.
 * Immortality - Like other angels, Samandriel can potentially live forever, despite torture methods that would definitely kill a human.
 * Superhuman Endurance - Samandriel has an above-human pain threshold and can endure torture.
 * Telepathy - Samandriel was able to contact Heaven telepathically, through "angel radio".

Trivia

 * Samandriel's name is an alteration of Samandiriel, the Angel of Imagination, known through visualization and thought to aid in transforming the world around us.
 * The actor who portrays Samandriel, Tyler Johnston, also appeared in the Season 1 episode Bugs as Matthew Pike.
 * Samandriel appears to hold humans in higher respect than most other angels. This may be due to his admiration for Castiel.