My Husband is Weak by Day, Strong by Night

Meredith is the illegitimate daughter of a duke. Scorned by her own family, she is shocked to hear that they have arranged a marriage for her–with no other than the Emperor of Valtzein. She soon learns that His Majesty has been placed under a curse and is weak during the day, returning to his former self only at night. When he tries to kill her on their wedding night, she strikes a deal with him–she will find a way to use her healing magic to break him free from the curse, in return for a divorce. But the Emperor has other thoughts–he's slowly fallen in love with her, and he won't let her go without a fight.