Alastair

Alastair is a white-eyed demon who, seemingly, is able to travel from Hell to Earth and is off the same statue 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. His current status and location is unknown.

Invulnerability
Unlike other demons, Alastair seems to be partially immune to Ruby's magical knife, however, he still get injured when stabbed by it.

Appearances

 * "I know what you did last Summer"
 * "Heaven and Hell"