Wolverhampton pulled off the biggest turnaround in the 20-season history of the Elite League at Monmore Green as they overcame a 12-point first-leg deficit to beat holders Poole.
Pirates' three-year reign as champions was ended when they were beaten 94-86 on aggregate in the semi-final.
Poole won last Wednesday's first leg 51-39 in Dorset.
But, after losing the second leg 55-35, Pirates boss Neil Middleditch said they "paid the price for underperforming".
Poole were forced into using their reserve riders after Swede Antonio Lindback was ruled out through illness, and Dane Bjarne Pedersen suffered a twisted knee while riding in Sweden.
"If the boys had all fired together, we could have done it," he told BBC Radio Solent. "We just don't know what kind of difference someone like Antonio could have made.
"I'm bitterly disappointed to be honest. I knew it was going to be tough here. But we just didn't perform. Too many of our riders just didn't come to the show. We just weren't good enough."
Belle Vue next up for Wolves
Wolves now face Belle Vue in next week's two-leg Grand Final, starting with Monday's first leg at Monmore.
"We have the fire power to rattle Belle Vue," said Swedish Peter Karlsson. "We have the form for the final."
Karlsson, who has ridden on and off for Wolves since 1990, was part of the squad that won the title in 1996, 2002 and 2009, the last two of which were in the Elite League era.
And, at 46, he admitted he had considered winding down his riding career this season.
"I wasn't planning to ride in England this year, as I wanted to ride less. I must have turned down 10 clubs in the winter," he added. "It was only Wolves. I didn't have to think more than two seconds."
"Whatever happens now in the final, it's already a successful season for us after a couple of lean years," said manager Peter Adams. "We're back in the big time and we're intent on staying there."
The Elite League's best comebacks
Although British speedway's Elite League started in 1997, the first two-legged play-off final was held in 2002 - and two-legged semi-finals were introduced in 2009.
In that time, Wolves' win was the largest first-leg deficit successfully overturned in a two-legged Elite League match.
The previous best was Poole themselves in the 2013 semi-final, when they came from 10 points down against Swindon to win the home leg by 17.
Wolves manager Adams, chasing a third Elite League title, told BBC WM: "It was a fantastic turnaround. A record-breaking overturn, but we always had the confidence we could do that."
Adams has won eight titles as a manager, two with Coventry (1978 and 1979) and two with Cradley Heath (1981 and 1983), before his four with Wolves (1991, 1996 and their two Elite League triumphs in 2002 and 2009).
And other great sporting comebacks . . .
Aintree, 1973 - After leading all the way round in the Grand National, and still by 15 lengths at the final fence, Crisp is overtaken on the line by Red Rum.
Vicarage Road, 1980 - Watford turn round a 4-0 first-leg deficit to win 7-1 on the night and beat Southampton 7-1 in the League Cup second round.
Headingley '81 - An Ian Botham-Bob Willis-inspired England rally from 135-7 in their second innings, still trailing by 92, to beat Australia by 18 runs.
Wimbledon, 1987 - Jimmy Connors comes from 6-1, 6-1, 4-1 down in the fourth round to beat Sweden's Mikael Pernfors in five sets.
Crucible, Sheffield, 1992 - Stephen Hendry trails 14-8 in the World Snooker Championship, but reels off the next 10 frames to win Jimmy White.
Rich Stadium, Buffalo, New York State, 1993 - Buffalo Bills trail Houston Oilers 35-3, but come back to win 41-38 in overtime.
Istanbul, 2005 - Liverpool trail AC Milan 3-0 at half time but score three times in five minutes to win the European Cup for a fifth time.
The Miracle of Medinah, 2014: Europe come back from 10-6 down after the second day to beat the United States in the Ryder Cup.