Wo Zai Hou Gong Dang Da Lao

Once upon a time, in a kingdom far, far away, there was an emperor who had it all - a handsome face, the highest authority, and a harem with three thousand beauties. But there is one thing missing from his seemingly enviable life - an heir. This was when Yun Mian, a fertility fairy from the celestial court, came in handy. To get a promised promotion for herself in the celestial court, Yun Mian descended to the mortal world determined to help the emperor carry on the royal bloodline. But things became a little tough when the emperor claimed to be impotent...
(Source: WebComics)