Time to introduce some new people and revive some scrapped ideas for the backstory of Alice.

Remember when i said Alice lived in some kind of fantastic world where monsters live, but humans never dare to go? I first intended this place to be the "afterlife" where the souls go to limbo and if they trespass the monster's territory it will be punished, this will make a direct analogy of hell. But since there are living humans (or souls?) who get past the monsters to see Alice, there must be something that makes a leakage of population the two worlds.

Who made this portal? There are many: magicians, warlocks, witches, acolytes, yadda yadda... what if scientists too?

...And then this is when skeleton buddy dressed with a scientist apron gets in the game. His name is Morton Ortiz, also known as "M.Ortiz", a scientist who used to be human (duh), and his greatest interest was to find out what happens after death. After research and research he came out with a portal which was a reinvention of the ancient magical portals which the elders created to make contact with spirits. He later died murdered in a fire by extremist activists who protested his research as "anti-ethic" and "outrageous". His dead body and soul were transported to his portal and he woke up as he is now: a living skeleton lurking in the land of the dead.
He got interested in this world he began to study it. He is now living in the castle of Madame Medusa, mother of monsters and demons, which is located in the middle of nowhere in a cliff. He works for the creation of new devices and new creatures thanks to his research of genetics in this world.

Alice was born thanks to him when in one day he wanted to create a pretty lady to make company for him, despite he was supposed to create ferocious and fearsome monsters in order to defend the castle from strangers. However, some dragon essence accidentally fell to the mix and a weird dragon-human female was born. He didn't want to kill her, but raise her as his daughter. Madame Medusa instead of punish him for making this "failed" experiment, she agreed he could keep her as his child. But: She would live away from the rest of the monsters in the highest tower in order to avoid the others make fun of her because of her lack of "mounstrosity" and "violent behavior".

She grew up dreaming and fantasizing about the human world her father talked about. She works as an assistant for his research work, in exchange to lend her the portal in order to explore the human world where pressumably she will be "accepted". And it happened: some humans were allured by the strange lass and they spread the rumor of the lady in the tower away in the unknown. Making humans to invade the forbidden land and madness happens, the portal must be held as a secret so he won't get fired.
Alice's biggest dream is to become a princess, although she is in fact a dragon.

...And that's it. Wait: Who's this dino-bird thing in the left? Well, he's a pet M.Ortiz created an named him "Feathers". He wishes to have lips, and to be a frog.

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TL;DR: This skeleton is a dead scientist who was transported to the spiritual world when he died, he created a portal which bonds both worlds and also he makes monsters for the queen of the land. He accidentally created Alice and he raises her as her daughter, she borrows his time/space/dimensional portal to take a walk to the human world.