The goddess of fertility has summoned one of her servants, a paladin, to commune with. She thanks him for his many years of service. He vowed to preserve life and he has done so, even breeding some maidens along the way as his goddess instructed. Now he returns home and as a reward, she gives you her body. However, this is also good for her as she wants to lead by example and have children of her own. They will in the future help spread her will even further. Not to mention, the breeding process is a lot of fun in itself. And what mortal is more worthy of her than you?