The climax involves coordinated efforts from multiple groups:
In the Season 3 finale of Stranger Things , titled the characters split into separate teams to stop the Mind Flayer and close the Russian-built gate to the Upside Down. The Three-Pronged Attack
They infiltrate the Soviet base to destroy the machine opening the gate. A critical moment occurs when they need Planck's constant for a code; Dustin calls his girlfriend Suzie , leading to a famous duet of "The NeverEnding Story" before she reveals the number.
From a radio tower on a hill, Dustin and Erica guide the adults through the Russian underground facility.
Trapped in Starcourt Mall, they face the massive physical form of the Mind Flayer. Because Eleven has lost her powers, the others use fireworks to fend off the monster. Major Sacrifices Stranger Things Season 3 Ending Explained - Time Magazine
