The new gate opened in Hawkins plays a crucial role in the story of the Spider Monster, also known as the Mind Flayer in Stranger Things. This gate serves as a portal between the Upside Down and the human world, allowing the Spider Monster to travel out of its dimension and into ours. The gate's existence and the subsequent formation of interconnected tunnels beneath Hawkins essentially provide the Mind Flayer with a pathway to infiltrate the town, leading to the events of Stranger Things Season 3. The gate's opening also causes power surges and outages in East Hawkins, hinting at the immense power and influence of the Spider Monster.