The Mind Flayer and the Demogorgons from Stranger Things share a unique relationship. They are all part of a hive mind, meaning they are interconnected and act according to the same collective consciousness. The Mind Flayer, being a malevolent entity from the Upside Down, uses this hive mind to control the Demogorgons and carry out its plans. This relationship was particularly evident when the Mind Flayer attempted to eradicate humanity in 1984, using the Demogorgons to execute its bidding.