These demons from Hindu mythology haunt cremation grounds, and can change shape and turn invisible. Often they possess humans in order to drive them insane. Obviously connected with the revenant vetala. Dad had this comment:
Reminded of the unnamed demon in the TESTAMENT OF SOLOMON who creeps “beside the men who pass along among the tombs, and in untimely season I assume the form of the dead; and if I catch any one, I at once destroy him with my sword. But if I cannot destroy him, I cause him to be possessed with a demon.”