Okay so Mike is they key/heart/missing piece to wills heart to defeat vecna.
Hoppers talking about the missing puzzle piece, pans to mike when it says puzzle piece. The scene with him looking into the room with the puzzle w the rainbow.
Will has an X over his heart while hes standing behind the whiteboard plan. While Holly says, M marks the spot. M=Mike.
Mike is the HEART. not just the heart, maybe Wills heart. Also mike has always been the heart of the party, since s1 he HAS to play more of a part than this is the finale.
Season3, hoppers saying Mike is the key. Maybe he has been all along.
Will saying in the future he ends up pushing everyone away because he feels different, like mike pushing everyone away and being distant this season and s3 and s4. He's been very emotionless this season until wills coming out scene, he starts almost crying. Some of the first decent emotion we see.
Mike WILL have to be the missing key/piece/heart to wills heart, meaning we need a confession for sure.
All proof right here
















