The Sexy Witches are humanoid Monsters kept in the Facility. They are listed on the Whiteboard, and the Archives department bets on them. It is unknown if they were released during the System Purge, or when.
Physical Descriptions and Characteristics
The Sexy Witches are presumably regular women who practice witchcraft and other forms of magic, but take-on a more seductive and alluring appearance. This itself could be a weapon to the Sexy Witches, seducing their victims as a distraction in order to kill them. This might also be the only thing that separates the Sexy Witches from the regular Witches, but it is also unknown if they share the same magical abilities such as stealing the souls. Since the Sexy Witches are not seen during the Purge or even in their Cube Prison(s), their appearances and how many of them there are is not known. If their magical abilities do in fact have a darker source behind them, this is likely why they are kept in the Facility.
A variety of items could summon the Sexy Witches, such as crystals, a love potion, Tarot cards or a crystal ball among many stereotypical modern-day magical items.
The Sexy Witches are not seen during the System Purge. It is unknown if they can be spotted during the scene where the camera pans-out to reveal all the Monsters of the Facility, as their appearances remain a mystery.
Sexy Witches could be considered a standalone horror trope with such notable appearances as the four girls from The Craft, Angelique Bouchard from Dark Shadows, The Witches of Eastwick (which also featured actor Richard Jenkins, who played Sitterson), Sarah Sanderson from Hocus Pocus and Morgan le Fay from the Arthurian Legends. Notable non-horror examples would be the Halliwell Sisters from Charmed, Sabrina and her aunts in Sabrina, the Teenage Witch, Samantha Stephens from Bewitched, Willow Rosenberg, Tara Maclay and Amy Madison from Buffy the Vampire Slayer, or Hermione Granger from the Harry Potter film series.