Chayagrahi means shadow grabber and is a demoness mentioned in the Kamba Ramayana. Her story is mentioned in the Sundara Khanda of Kamba Ramayana. She meets her match in Hanuman who was jumping across the sea to reach Lanka.
Chayagrahi had her home in the ocean and she used to feed on the birds that flew above the ocean. She used catch the birds flying overhead by grasping their shadows in the water. She used to then pull down the birds and feed on them.
She was thus living happily in the ocean.
But she made a mistake by trying to capture Hanuman who was flying over the ocean. She grasped the shadow of Hanuman and tried to pull it down.
Hanuman killed her with a blow of his left foot and sprang forward towards Lanka.