Alastair

Alastair is a white-eyed demon who, seemingly, is able to travel from Hell to Earth and is of the same stature as Lilith. Dean first encounters Alastair in Hell and is the one in charge of torturing him. Each day, for 40 years, Alastair would ask Dean if he wanted to trade his place for another soul. For 30 years, he refused and, each day, was chopped and killed and then placed back together, only for the cycle to continue. He couldn't bear the pain much longer and, for 10 years, tortured souls.

Alastair resurfaces on Earth to try to capture Anna Milton and use her gift for their gain. Although his initial attempt was unsuccessful, he manages to get a hold of Ruby's magical knife.

Later, he returns and strikes a deal with Ruby, who promises Anna for the safety of the Winchesters and herself. Alastair, after torturing Ruby, accepts. Unknowingly, however, he falls into a trap set by the Winchesters and later vanishes after Anna regains her grace. He returned a short while later, possessing a new body. He was behind the abduction of a reaper in a small town. He encountered Sam and Dean and fought them, Sam was able to force Alastair to leave that body. He gained a new one soon after and abducted a second Reaper named Tessa who the Winchesters knew. He planned to kill the two reapers on the night of the solstice to break another of the 66 Seals that needed to break in order to free Lucifer. He failed, only being able to kill one reaper, and was captured by the angels.

After seven angels were killed, Castiel recruited Dean to torture information out of Alastair. Alastair simply mocked the fact that his former protege would be the one to try and break him. Alastair revealed that the first seal was broken when Dean gave in in Hell and began torturing people. This explained why the angels had rescued Dean from Hell. Alastair managed to break free from the Devil's Trap he was binded in through water dripping from a pipe. He quickly tortured Dean and then beat up Castiel until Sam arrived and pinned Alastair against a wall using telekinesis. He hurt Alastair until the demon revealed that the demons were not behind the angel killings. Alastair then challenged Sam to excorcise him but Sam was now more advanced with his powers and simply used his abilities to kill Alastair in a similar fashion to what the Colt or Ruby's Knife would do. It was later shown that Uriel was behind the angel killings.

Invulnerability
Unlike other demons, Alastair seems to be partially immune to Ruby's magical knife, however, he still gets injured when stabbed by it. It is shown in "Death Takes a Holiday", Alastair is susceptible to Sam's demonic powers even though he was not when the two first met.

Appearances

 * "I Know What You Did Last Summer"
 * "Heaven and Hell"
 * "Death Takes a Holiday"
 * "On the Head of a Pin"