EQUESTRIAN RED SIRLOIN is the Laundry code phrase covering the class of autonomes commonly referred to as unicorns.
Sub aspects of this code phrase include the breeding adult, adult drone female, male and female juveniles and subverted human female drones. There also appears to be the possibility of a breeding adult forming a psychic gestalt with an adult human male although the characteristics of this gestalt are not known to the Laundry and this aspect may not actually exist and may instead be a ruse used to lure human males in for feeding.
The Equoid case file covers the detection and eradication of a fully developed EQUESTRIAN RED SIRLOIN colony in rural England and includes an averted example of the breeding adult/human male gestalt discussed above.