speaking of Artemis and Lucifer

Artemis

A Savannah cat is a cross between a domestic cat and a wild African cat.
Savannahs are commonly compared to dogs in their loyalty, and they will follow their owners around the house like a canine.
Some Savannahs [...] may run and hide or revert to hissing and growling when seeing a stranger.

An often-noted trait of the Savannah is its jumping ability. They are known to jump on top of doors, refrigerators and high cabinets. Savannahs are very inquisitive, and have been known to get into all sorts of things. They often learn how to open doors and cupboards, and anyone buying a Savannah will likely need to take special precautions to prevent the cat from getting into trouble.

Many Savannah cats do not fear water, and will play or even immerse themselves in water. Some owners even shower with their Savannah cats. Presenting a water bowl to a Savannah may also prove a challenge, as some will promptly begin to "bat" all the water out of the bowl until it is empty, using their front paws.

Another quirk Savannahs have is to fluff out the base of their tails in a greeting gesture. This is not to be confused with the fluffing of fur along the back and full length of the tail in fear. Savannahs will also often flick or wag their tails in excitement or pleasure.

Vocally, Savannahs may either chirp like their serval fathers, meow like their domestic mothers, both chirp and meow, or sometimes produce sounds which are a mixture of the two. Chirping is observed more often in earlier generations. Savannahs may also "hiss"—a serval-like hiss quite different from a domestic cat's hiss, sounding more like a very loud snake. 

It can be alarming to humans not acquainted to such a sound coming from a cat.

- Enciclopedia Galattica Universale