It kinda started as practice while I was listening to an audio Uni lesson.

The way I see it he is like an inverted dorian gray. he made a pact to a cosmic force who feeds on good deeds and positive spirits, as in morally pure actions. basically he wanted prosperity for his kingdom, and the force promised so as long as the king kept his heart pure (so that it would feed off him). he accepted. he was a good king, and his kingdom prospered, but the more pure he acted, the more his body rots away. the only way he could save himself is through corrupt actions, however he is so pure of heart he is unable to refuse betraying his morals, and so he keeps rotting.