Xills are a race of evil outsiders native to the Ethereal Plane.
Feral Xill: One in ten young produced by a standard xill is hatched without the ability to planewalk. Standard xills summarily kill any such young that hatch on the Ethereal Plane, seeing them as defective creatures unworthy of life, but those hatched on the Material Plane sometimes escape into the wild. These feral xills grow to adulthood without the benefit of a true society, developing neither tools nor language.
Predatory Xill: One in ten young produced by a standard xill is sterile, lacking the ability to paralyze victims and implant eggs. Unable to propagate the species, these xills are relegated to the fringes of xill society, where they find purpose in a religious practice revolving around ritualistic trophy hunts and complex codes of honor. These so-called predatory xills make regular forrays into the Material Plane to hunt dangerous creatures such as seasoned adventurers and feral xills.