His clear intelligence, kindness, appreciation for the arts and sensitive soul really do it for me. Love that he plays the lute and writes poetry. Not to mention, I absolutely cannot resist a damoiseau in distress, much less an extremely hunky one.
(I'll be honest, he's a teeny bit too stacked for my preferences? Not that it's unattractive! I just prefer the more modestly buff form he has a couple of days in.)