Somewhat like a cross between Gravity Falls and Rick and Morty.
At first, it appears as basically a light comedy. The first season is reasonably light, episodic, and silly. Then it gets darker. Much, much darker, and much more emphasis on the overarching plot.
It is a sort of deconstruction of “princess” and “magical girl” tropes.
The lead character is a princess from another dimension and heir to the throne of her kingdom who has been given, as is traditional there, a powerful magic wand - but she is dangerously reckless with it. So her parents exile her to Earth, so that of she does any damage, it will be to Earthlings and not her own nation. Naturally, there are some bad guys - monsters - who are out to steal her wand.
In the first couple of episodes, it appears the show will have a standard recurring plot - the monsters try to steal her wand, and with the help of her Earth friend Marco, she easily kicks their asses. The monsters appear essentially cute, ineffectual and harmless, lead by a diminutive villain who is hopelessly outclassed.
However, this is merely the background set up for the actual storyline. Nothing is as it appears. One of the central themes of the show is that appearances can be deceptive.
[spoiler] While the lead character Star appears to be an excessively cute 14 year old girl, she is in fact genuinely dangerously reckless - and has been trained to kill from a young age, and has done so, frequently. Her family turns out to be more “Game of Thrones” than “Disney”.
Moreover, they are fundamentally alien. This is highlighted when Star goes through an alien version of puberty - with horrifying results, somewhat reminiscent of the movie Alien.
The monarchy she represents appears to be the “good guys” and the monsters the “bad guys”. Star has certainly been brought up to believe that, but it proves to be mostly untrue. Her people simply moved into the monster’s lands and massacred them, colonialist-style, when they attempted to resist. Star gradually comes to understand this.
The apparent leader of the monsters is ineffective - but not all of them are. In the second season, the sufferings that Star puts that leader through are highlighted; he becomes a much more sympathetic - and terrifying - character. [/spoiler]