So I noticed that eddie only used his upside down guitar, meaning another copy now exist in his trailer. Since music seems to be a pretty all around way to trigger the positive energy needed to defeat the upside or however that whole situation is working, im wondering if that guitar is gonna play some significance later. I could see Dustin becoming like Eddie by season 5 and playing that guitar. I think it could also be a good Stranger Things analogy for the "sword of kas". I could even see Dustin learning to play some metallica just in time for vecna to get stomped in season 5. Maybe some "for whom the bell tolls" to honor our fallen heroes.