On Supernatural Season 13 Episode 3, Sam wasn't sure if Dean was completely OK despite Dean assuring Sam he was until Dean noticed a scar on his arm. He immediately consults with Sam and Castiel about the scar and they reach out to Jodi for help. When Dean describes the scar to Jodi she immediately knows what he is talking about because she has three bodies which washed up without their heads with the same scar. 

Sam and Dean go to Jodi and they hunt down the person who has the spear. They are surprised to learn other world Kaia is the one responsible for having the one weapon which could hurt Michael. Kaia explains Michael tried to make a deal with her because he knew she was strong but when she tried to kill him with the spear he learned she was stronger then he realized. Eventually Michael makes all of his creatures go after Kaia so he can be in control of the spear but Kaia has taken every single one of them down. 

Kaia explains she won't be turning the spear over to Sam and Dean because she is OK with having the monsters coming after her. Dean explains to Sam he is to blame for everything going on because he said yes to Michael. It doesn't matter what anyone says to him or how they spin it, Dean feels as though he is the one at fault. 

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