Cat Sìth

The Cat Sìth is a fairy cat of the Sidhe that haunted the Scottish highlands with it's dog-like counterpart, Cù Sìth, both would steal the souls of humans, although unlike the Cù Sìth the Cat Sìth would take the souls from corpses awaiting burial.

Appearance
The Cat Sìth had the appearance of a slender, black cat about the size of a dog with a small white spot on either it's belly or near it's neck, it's back is usually arched and it's fur erect as a normal cat would do to show dominance.

Known Cat Sìth

 * Tom Tildrum - a house hold cat that was presumed to be a Cat Sìth due to his ability to talk, escaped his family home via the chimney after finding out that Tim Toldrum was dead and that he is now King of the Cats.
 * Tim Toldrum - a Cat Sìth that was the King of the Cats until his demise, the owner of Tom Tildrum spotted Tim Toldrum's funeral in the woods.
 * Big Ears - A demonic Cat Sìth that would answer any question and fullfill any wish the summoner may have, summoned on Taghaim when if several cats were burned alive on a bonfire each night for four days. Presumably took pleasure in seeing his fellow cats burnt alive.

Deeds and Personalities
The Cat Sìth were well known for stealing the souls of the unburied dead and commonly preyed on funeral parlours and such places where the body is prepped before burial.

The denizens of the highlands would ward off the Cat Sìth with riddles, music and catnip among other things, they would also keep the corpse in a cold room as the Cat Sìth was attracted to warmth.

On Samhain (Halloween) the Cat Sìth would often prowl dairy farms and steal the milk from cows, rendering them useless, people would prevent this by leaving out bowls of fresh milk for the Cat Sìth.

Overall, the Cat Sìth prefered the warmth, were easily distracted, bitter if they weren't shown respect and, in some cases (Big Ears), they enjoyed the torture of fellow cats.

Ireland
In Irish mythology the Cat Sìth was not a fairy but instead a witch who could turn into a cat a maximum of nine times, with the ninth they would be stuck as a cat forever.

This was probably the source of the "cats have nine lives" wive's tale.

Inspiration
It is commonly accepted that the Cat Sìth of the Scottish highlands was based off of the Scottish Wildcat, more specifically, the Kellas cat, a hybrid between common, domesticated cats and the Wildcats of Scotland.

This fits the description of the Cat Sìth being both dangerous and feral yet in some cases being used as household pets.