She is the Celtic ruler of the Underworld until then, her kingdom is not enough for her anymore, so she seeks to conquer the Earth by creating an eternal Halloween.
Carlin, as ruler of the Underworld, was quite evil, ruthless, villainous, arrogant, power-hungry and confident in her powers. Driven by a need to conquer, she sought to extend her kingdom and rule the real world by creating an eternal Halloween. She put on a welcoming facade to trick humans into eating her chocolates and turn them into her minions. When Martin and his gang confronted her, she mocked and saw them as "annoying" and "obnoxious".
Role in the episode
During one such Halloween night, a Scottish woman, Katie came into Paddy O'Brian's store for her possession of a necklace bearing the Carlin's seal. Once she put it on, it allowed Carlin passage into our world and she possessed the wearer of her necklace. She began planning her takeover of the world by planting her seal on chocolates which she then gave to Trick-or-Treaters who came her way. The magic inside the treats caused the people who ate them to turn into their costumes as well as making them her slaves.
When Martin, Diana and Java showed up on her doorstep and confronted her, she fought back. During the skirmish, the necklace was snatched away from her and her host was freed with no memory of her actions while under Carlin's control. However, Martin, who had eaten her chocolates and turned into a baby, grabbed the necklace, put it on, and became possessed by Carlin. Subduing her again, Diana thought about destroying her pendant but was stopped by Billy (who was wearing a costume like Martin), who explained that breaking it would only trap Carlin in our world.
The group then decided to feed Carlin her our chocolates, hoping it would have an opposite effect on her. And it did. Carlin was forced to leave Martin's body and was banished back to the Underworld. All traces of her presence vanished and the people she had affected returned to normal.
Powers and Abilities
As a spirit of the Underworld, Carlin has numerous magical powers. Any magic she cast had a permanent effect as long as she was present on Earth. Once she was banished, all traces of her presence vanished and everything returned to normal. During the episode, she displayed the following supernatural abilities:
- Immortality: As a spirit, Carlin is eternal. The only guaranteed way to defeat her was to send her back to her own realm before dawn, otherwise she would be able to remain on Earth forever.
- Possession: Carlin could take control of any human who wore the necklace bearing her seal. Even if the necklace is removed from her host, any person who is affected by her magic will take it and wear it, becoming her next host. This proves that her pendant acts as both a portal and an anchor for her to our world. However, destroying it only traps her on Earth forever.
- Shapeshifting: While possessing a human, Carlin could turn into a giant raven to fly and attack her enemies. She could also turn into a flock of smaller ravens and back again. She was also able to transform into her real, grotesque appearance.
- Transformation: Carlin turned people into the monster they were dressed as. This was done by planting the seal of her necklace into chocolates. Once a person ate them, they became loyal to Carlin.
- Cryokinesis: She could fire blue beams from her hands. Anything they hit was instantly covered in ice and frozen solid.
- Her real name is the Cailleach (Irish pronunciation: [ˈkalʲəx], Scottish Gaelic pronunciation: [ˈkaʎəx]) which she is a divine hag, a creator, weather and an ancestor deity.