Blessings
In the universe of TOOLLA each person is essentially at the whims of their goddess, Lady Luck. Lady Luck is a very fickle goddess who likes to change massive things to her world and then ignore it for a while, but she's aware of how bad this attitude can be. To support her own behavior, she created beings that are essentially angels, named Storks. Storks manage the whole birth part of the death and reincarnation cycle that Lady Luck is supposed to oversee. Usually Lady Luck herself is supposed to bless the souls of new humans before they get sent down to the earth, which grants the humans with protection from things like monsters and demons, as well as grants them an insane amount of luck which can rub off on others. Storks will go around and bless souls for her, and she's kept it this way for a very long time.
If a child is blessed by a Stork they will be dubbed a 'Blessed', which gives them the physical appearance of having cat-like ears and a good amount of luck. Blesseds are essentially the modern-day nobility. The problem with this system, however, is that Storks aren't gods in timeless realms. They can't reach every single child especially with the rate at which human population is growing. If a soul is born without being blessed they receive no benefits. They are weak, they can't understand things easily, and are incredibly unlucky. Humans that have not received a blessing are dubbed a 'Devils Child' and will be born with incredibly sharp horns. If a woman gives birth to a devils child, the horns likely either kill or disable her, which is the start of their very unlucky life.
Black Cats, however, are a different story. Black Cats are people who are personally blessed by Lady Luck, which gives them that massive advantage of a whole lot of luck that can rub off on others. Black Cats look exactly like Blesseds, however they will be born with black hair. The Devil of this world noticed these humans and decided to play a trick. Occasionally he will also bless a child and it'll be born with the same appearance of a true Black Cat, but the child will have incredibly bad luck that will rub off on others. Humans noticed that Black Cats typically spell doom and will usually kill their child if they're born one.
Scientists have tried many studies and can't find any genetic evidence linking a parents blessing to a child's, making having a kid a whole gamble. Devils Children will have kids hoping they'll give birth to a Blessed that'll pull them out of poverty, and some Blesseds have managed to capture Storks to ensure their family will never bear a Devils Child.
Occasionally, Storks will be born from Lady Luck which will grant a different appearance. They have the same blessings but a different appearance depending on the whims of Lady Luck. The only known alternate-blessings are (ranked from most to least common) dog, hawk, koala, and shark. These alternates only affect around 1 in every 1000 people.