Royal Jelly.

Once upon a time, there was an empire where the sun never set. This empire had a court. This court had a king, but this king had no heir. They married the king, who understood that copulation was a duty of state and attempted it with exemplary dedication, but failed. The entire court, from the nobility to the jesters, gets down to work, sparing no means or methods, to produce the desired heir, and they reach a conclusion: the king has been bewitched and needs be exorcised.