Percy (Percival) is an extra-dimension magical being who is Shadowthief's familiar. On Earth, Percy takes on the appearance of a black cat.

Percy is ancient and has visited Earth many times in the past, including a long stint in Ancient Egypt and another during the Middle Ages, where she became acquainted with Dr. Darke. Percy can talk and from her many past trips to Earth is fluent in most languages.

Percy is Danika Darke's lifelong guardian and companion. Being from a shadow dimension, Percy has the ability to see in the dark, to cloak herself, and enter and move through shadows at will.