The Cats are both a spell and a magic item. Without the item, you can't cast the spell. If you have the item but can't cast spells, it's useless. They are one in the same.
The Cats of Corrooll are a set of carved stone cat statuettes. Each cat has a unique appearance, and underneath each in an ancient script is the cat's name and a ritual phrase. The phrase roughly translates to “We scream at night, but we are not afraid.” Every statuette has the same ritual phrase. You can cast the spell as long as you have at least one cat.
When the spell is cast, each cat you have present at the time of casting will turn its head towards you, and speaks through the statuette, though they do not truly become animate with false life. The cats all have their own names and are more then happy to engage with polite conversation with anyone who casts the spell- they are friendly, helpful, polite, and they even like to flatter or flirt with the spellcaster. They want whoever owns them to like them and protect them. They don't want to be destroyed or trapped in a place where they can never be found again- an eternity of darkness at the bottom of a great sea is a terrifying prospect to a motionless, immortal entity.
The cats only want two things. The first is to stay safe, and the second is to stay together. Each cat will try to subtly manipulate its owner to acquire more cats. Each one grants power to its owner, so having more of them makes their owner more powerful and, therefore, the cats are more safe.
The cats are made of carved stone and are quite tough. They cannot be destroyed by falls (as they always land on their bases) but can be with magic hammers or items, especially ones shaped or based on dogs.
Wherever at least one of the cats is being held; strange haunting begin to happen at night. Not in the same room, but in the city itself. Whatever town or village they are within, the cats will stalk. Every night they appear as formless specters, only appearing as a cat in the corner of your eye or from their frightening yowls. The cats examine the city, listen to every word spoken, watch sins committed through open windows, and sometimes even arrange accidents to kill people.
Every cat has a name and a voice. They can be made to move by speaking the incantation- the identical ritual phrase on each. Their heads will turn to look at the one who spoke it. The cats can then speak and tell the owner everyone and everything they have seen that night. Whatever the master wishes, they will tell him about. The cats have a strange memory- they can remember people, names, or commands but forget everything they have seen or heard when in their specter forms after the new moon. Their ability for spying is not unlimited; conversations held in windowless back rooms inside huge mansions will not be heard, unless it's a place a stray or wandering cat could reasonably roam.
For every cat you have in your collection, roll once each on your rumor/secrets table. You automatically know which rumors are true, or at least have a 4 in 6 chance to know if someone is spreading a false rumor.
You can also direct your cat's attention. Instead of gathering information, you can assign a cat an individual to keep tabs on. The cat will track their movements through the city, where they go or what they whisper if they are loud enough to be heard through a window or under a door. Especially wily marks, like rogues or elves, may require multiple cats to keep up with. Increase the number of cats you need by +1 if they know you're watching them as well.
Finally, as a last resort, the physical “bodies” of the cats can be used as a magic wand. Each cat statue can be used once per day like this, ejecting a black cat spirit with a hiss that deals 1d4+1 damage, save for half. Each cat statue you use as a wand cannot manifest that night, as this is exhausting.