Everything we’ve ever assumed about the Upside Down has been dead wrong.

The heroes of Hawkins may be bloodied and battered, but the “Stranger Things” Season 5 Volume 2 trailer assures us that the war is not over — not by a long shot.

The first four episodes in the long-awaited conclusion to “Stranger Things” are on Netflix now, with the next three episodes dropping on December 25 and the series finale — also in theaters — on December 31. Each volume releases at 5pm PT/8pm ET.

“We’ve always known that Will has a connection...