A link with the real world and the spiritual world. A familiar that travels on the other side - can be used good or evil depending on the Cat's owner, type of magic, message or mission the cat is send on. Witch's cats communicate with the dead since of all the animals they are the most senitive to the deads' presence. Usually a black or darker cat with intelligence and an attitude - not your normal house cat.
The witch's cat is a holleween favorite and a witch usually has one close at hand.
The witch's cat picked up his ears and refused to go into that room, he was aware of the spirits that were there.