From this post: 

“…are you simply content to remain as a mere portrait on Mr. Dorian’s wall~?”

‘The Picture of Dorian Gray’ is a novel from 1891 in which a young gentleman has his portrait painted by an artist, and is so in love with his own handsomeness that he sells his soul to remain young and attractive forever… embarking on a life of hedonism. But as he gives in to his vices, the portrait in his home reflects who he truly is… aging, twisting, becoming nothing more than a disgusting and corrupted version of himself.

By Hakubby calling Cleanba ‘the portrait on Mr. Dorian’s Wall,’ he’s saying that Cleanba must be a miserable person bearing the scars of sin without having experienced life at all.

…of course, in doing so, he’s admitting that he, himself, is far too addicted to his own vices.

Perhaps more interesting, it seems that Hakubby is so thoroughly invested in his hedonistic lifestyle that he is intent on corrupting his counterpart. Is it because he truly believes that Cleanba would benefit from experiencing more of life? Or is he envious of his other self for not being tainted with sin, unlike himself?

Hmmm~!