As seen in this eschergirls post, it’s a character from Tree of Savior. According to image file name, she’s called Dame Circe, which along with the glowing smoke in the background, suggests that she’s a knight and a magic user at the same time. How does it explain her having one of the most ridiculous attires out of many weirdly-dressed female NPCs in the game is beyond me.
Maybe she really does
breathe through her skin I mean, derive power from her breasts, as @eschergirls suggested? Nonetheless, we will probably never know how does this thing hold up.
PS: Is that a Soul Gem right under her cleavage?