I look at this painting today, and I'm still pretty much in love with how you've made Sedesna turn out. Definitely some of my best spent commission money.
In contrast to your other succubi, what sells her to me is her allure and mystique. She turns out being very feminine and sensual, but not as openly sexual, and that lends her an air of cultured maturity which shows contrasted diversity with your other work - I encouraged you to push for an 'older sister'-look in comparison to your other succubi and you definitely nailed it. She strikes very well upon what I'll call "Bride of Dracula" visual cues and this lends her an air of regality, something classical, to her.
Most succubi seduce mortals, but it doesn't look like Sedesna feels the need to. There's this nobleborn lady-like sense that she is not easily had, like some cheap wine. Her presentation shows enough to entice without exhibiting, and her expression in her hooded eyes more a challenge for the onlooker to do more than just covet her: to meet her expectations, to be of interest to her. Otherwise he can just go on with his dreary life as he has, a waste of mortal flesh all too much a victim of entropy and decay.