Wearing their Thor-inspired guernseys, the Western Bulldogs brought the hammer down in a stunning first half against Sydney before hanging on for a famous 17-point win at Marvel Stadium.
The Swans trailed by a game-high 40 points shortly after halftime on Saturday night and were still 32 points in arrears at three-quarter time before they slashed the margin to just four points with five minutes remaining.
But the courageous Bulldogs found a way to wrest the momentum as Marcus Bontempelli and Sam Lloyd kicked the last two goals in a pulsating 11.16 (82) to 9.11 (65) win in front of 32,303 fans.
Bontempelli was brilliant for the Dogs with 29 possessions and his vital late goal, with Jack Macrae and Tom Liberatore, in his first game back from a knee reconstruction, important with 32 and 28 touches, respectively.
Luke Beveridge stuck with rising star Aaron Naughton in attack and the versatile tall repaid his coach with three goals in an influential display.
"To find the energy just for that last six minutes it's a real credit to them because it seemed like we were out on our feet," Beveridge said.
"I thought our players did their best under some duress so that's a good sign for us."
Swans star Isaac Heeney had a superhero moment in the opening minute of the game when he took a contender for mark of the year, but the visitors managed just one goal for the half.
Heeney, last year's mark of the year winner, leapt onto the back of Bailey Williams and completed a spectacular grab and then booted his side's lone goal before the long break.
The rampant Dogs took control and stormed to a 33-point halftime lead before the almost-inevitable Sydney challenge came.
With Lance Franklin struggling to impose himself after groin surgery limited his preparation, Zak Jones (24 disposals) and Jake Lloyd (35) were the architects of the stirring fightback.
The hosts looked set for heartbreak as Sydney swooped with a run of four unanswered goals to open the last quarter.
"We were coming home with a wet sail," Swans coach John Longmire said.
"We needed things to go right after the start we had. We got close, we just couldn't quite kick that goal to put us in front."
The Bulldogs have an injury concern with Matt Suckling hurting his ankle after the oft-maligned turf at Marvel Stadium gave way under him.