Hux is Emperor and he's like the most powerful man in his corner of the galaxy. And then his ministers start making noise that he has to get married. He doesn't want to, but makes a law that he will only marry someone who can answer three riddles and if they fail, he has their heads chopped off.

Suitors start coming because Hux is fine but none of them can answer his riddles because Hux created this rule because his riddles are impossible and he doesn't want to get married dammit. And then Kylo, who is royalty himself, decides he'll try his hand because A) he's been pining over the Emperor for a long time and B) he's a Force User. He shows up at the palace, the Emperor places his riddles, and because Kylo can read his mind, he answers them no problem.

"Well shit," says Hux, and has to deal with actually following through on his own law and deal with marrying this guy.