Real Name: Meg
Location: Hell (originally & exorcised to in 1.22 Devil's Trap), Earth (2007 & currently)
Occupation: Black-Eyed Demon
Actresses/Actor: Nicki Aycox, Jared Padalecki, Rachel Miner
Episodes: 1.11 Scarecrow, 1.16 Shadow, 1.21 Salvation, 1.22 Devil's Trap, 2.14 Born Under a Bad Sign, 4.02 Are You There, God? It's Me, Dean Winchester (referred to), 5.01 Sympathy For the Devil, 5.10 Abandon All Hope
Sam has left Dean and is traveling to find his father in California when he encounters Meg Masters, who is also hitch-hiking. their first encounter is brief, as she soon gets a lift with "sleazy van guy". She later turns up at the bus station and she and Sam bond over feeling trapped by their families' expectations. Meg tries to dissuade Sam when he leaves, concerned Dean is in trouble. At the end of the episode, Meg is again hitch-hiking. She gets the driver to pull over and then cuts his throat with a dagger, collecting his blood in a goblet. She swirls the blood with her finger, and after a Latin incantation, communicates with someone she calls "Father". It is revealed that she was well aware of who Sam was.
The boys run into Meg in a bar in Chicago. Sam is immediately suspicious of this coincidence and follows her, finding she has a black altar set up in an abandoned warehouse, and is controlling the daevas. She again uses the goblet of blood to communicate with someone she reports to. The whole set-up is a ploy to lure John Winchester and the boys to Chicago, but she fails despite capturing Sam and Dean when her altar is destroyed and the daevas turn on her. She plummets from the building many stories down to the sidewalk. However at the end of the episode, she is seen alive and well, watching the Winchesters go their separate ways.
Meg murders John Winchester's friends Pastor Jim and Caleb, in order to force him to hand over the Colt. She gets John to come to a warehouse in Lincoln, Nebraska on the corner of Wabash and Lake. Her he hands over a fake Colt, which is discovered when Meg's "brother" Tom shoots her with it and she doesn't die. She and Tom then capture John Winchester.
1.22 Devil's Trap
Meg calls Dean to reveal she is holding their father. Later she tracks them down at Bobby's place, but is captured under the devil's trap. Sam starts to exorcise her, while Dean interrogates her as to their dad's whereabouts. Bobby points out to them that she is actually a woman possessed by a demon, and that because of the injuries she sustained in Chicago, will die when the demon leaves her. The demon leaves, but the human, dying, Meg tells Sam and Dean where John is being held before she dies.
2.14 Born Under a Bad Sign
The Meg!demon has been in hell - which she describes as "It's a prison, made of bone and flesh and blood and fear". She has escaped to possess Sam, planning to kill hunters and to try to provoke Dean into killing Sam. It no longer gives a "rats ass" for the plans of the The Yellow-Eyed Demon. While possessed by the demon Sam's smokes menthol cigarettes and drinks hard liquor. While in Sam's body she kills a hunter, Steve Wandell, and using Jo for bait, nearly kills Dean. It goes after Bobby, but her possession of Sam is revealed when Bobby gives her beer laced with holy water.
Bobby and Dean trap her beneath a devil's trap, but they find it difficult to exorcise because it has used a spell to bind itself to Sam's body. Bobby finally burns across the binding brand, and the demon is exorcised, but not sent to hell. It escapes.
4.02 Are You There, God? It's Me, Dean Winchester
Lilith casts a spell that breaks one of The 66 Seals that holds Lucifer captive and releases the Witnesses - ghosts who return and kill those who let them die. Meg Masters returns and confronts Dean. She tells him how she was a college student when she was possessed, and that she was 'awake' during her possession, and witnessed much horror. She also tells him how her disappearance had a terrible affect on her younger sister, who killed herself after Meg was found dead. The spirit of Meg Masters is vanquished when Bobby completes his spell.
5.01 Sympathy For the Devil
When Dean works out the meaning of Chuck's message about the location of the Michael Sword, Bobby attacks him, revealing he is possessed by a demon. At that point Meg arrives, informing Dean that the demons want him dead so he can't stop Lucifer. She orders the possessed Bobby to kill Dean with Ruby's Knife, but just as he is about to strike, Bobby manages to battle the demon and stab himself instead. Sam returns and helps dispatch the other two demons, but the Meg!Demon escapes by leaving her vessel.
5.10 Abandon All Hope
Meg apparently recovered her vessel and has joined forces with Lucifer after her encounter with the Winchesters, following Lucifer to the city Carthage. Upon Lucifer's orders, Meg confronts Sam, Dean, Ellen, and Jo in the streets of Carthage, setting a pack of Hellhounds on the group; one of which grievously wounded Jo.
The hounds cornered the group in a store, and so Meg returned to Lucifer's side to ask for further instructions. He told her to leave the brothers be, however, and left her to watch over Castiel, whom Lucifer had trapped within a ring of burning Holy Oil. Meg gleefully reveled in the fact she and her kind were "winning", but Castiel quotes the demon Crowley's message: that Lucifer cares little for demons and merely sees them as a means to an end and will kill them soon after the humans are eradicated.
Meg does not believe him, however, though falls for his duplicity as he telekinetically swings a large pipe into her, knocking Meg into his arms. Castiel immediately tried to exorcise her with his touch, but his power fails him as he is cut off from Heaven. Meg taunts Castiel, asking what he plans to do now that he is powerless. Castiel replies by throwing her onto the fire, and as she screamed in agony, walked over her body like a bridge and escaped from captivity.