The final boss of the Valley of Defilement is Maiden Astrea, a pure-souled woman who discovered God's true excistance. She set out for the Valley Of Defilement in order to help with the plague; but she never returned. There, she accepted the soul of a demon in order to ease the troubled. Thereafter, her soul is said to have become impure, and it is a huge conspiracy if she's actually evil or not. What makes this boss unique to the series is that the boss is difficult, whitout actually having to fight it. She actually commits suicide after you murder her loyal follower Garl Vinland, who claims that you shold leave quietly, and leave Astrea alone. "This is a sanctuary for the lost and wretched. There is nothing here for you to pillage or plunder. Please, leave quietly"