Board Thread:General Discussion/@comment-25532617-20141013053613/@comment-24862674-20150730054027

And when you defeat it there is an explosion of darkness around the boss and the darkness clears up to reveal an npc that said she was cursed by a very powerful dark spirit and she will come into an available house. Also, the corruption/crimson stops spreading because after defeating the dark spirit, the player has weakened the evil and darkness in the world.