They may have not dominated proceedings but a clinical defensive performance by the Crusaders ensured them a 27-13 win over the Chiefs and a place in the final.
The Chiefs had all the possession and ample opportunities but Crusaders' defensive display kept the visitors at bay.
The seven-time champions Crusaders scored four tries courtesy of Bryn Hall, Israel Dagg and a brace by Seta Tamanivala, while the Chiefs scored one try thanks to Brodie Retallick.
The Crusaders could have a home final at Christchurch, depending on the results between the Lions and Hurricanes.
With the Crusaders up only 10-6 at half-time and starved of possession, the game turned 10 minutes into the second half when Chiefs wing James Lowe attempted a clearing kick while scrambling on defence.
Mo'unga came from behind to knock the ball into the hands of the oncoming Dagg, who dived across the line to open up the Crusaders' lead and from there they never looked back.
Tamanivalu, who this week turned down an offer to return to the Chiefs and will stay instead with the Crusaders, added two more tries before Retallick scored a consolation five-pointer for the Chiefs at the end.
The Chiefs enjoyed 77 percent possession in the first half and the Crusaders were forced to make 200 tackles in the match, but captain Sam Whitelock said they always felt the game would turn.
"The Chiefs held the ball and really attacked us, especially in that first 50 minutes," he said.
"We knew if we could weather that storm we'd hopefully come over the top of them in the end."
Chiefs captain Aaron Cruden, in his last game in New Zealand before taking up a contract to play in France, said his side had enough possession to win but could not find their way to the line.
"You've got to give credit to the Crusaders. They scrambled really well and when it looked like we had them on the ropes they were able to just do enough to hold us out," he said.
The Chiefs, despite returning from a long trip to South Africa where they beat the Stormers last week, looked more rejuvenated at the start despite their inability to cross the Crusaders line.
Matt Todd cut down Cruden from behind early in the match, Tim Nanai-Williams spilt the ball when diving for the line while Lowe was also brought down short of the line just before half-time.
The Crusaders struggled in the possession stakes but they made the most of their limited chances, hitting the front with a Mo'unga penalty the first time they made it inside the Chiefs' 22.
Dagg engineered the only try of the half when he sparked a counter-attack from deep in Crusaders territory and worked with Ryan Crotty to sweep down field before scrumhalf Bryn Hall finished off the move.
Mo'unga converted the try while Damian McKenzie brought the Chiefs into the game with two penalties for the visitors to trail by four points at the turn.
After Dagg's try extended the lead for the Crusaders early in the second half, Tamanivalu crashed over twice to put the game beyond doubt at 27-6 before Retallick scored the Chiefs' only try at the end.
Man of the match: Damian Mckenzie's brilliance has become a mere formality, the fullback precision kicking and counter-attack kept the Crusaders' defence busy, while in front Brodie Retallick added the muscle. On the Crusaders' side, Kieran Read's work rate proved to be vital the side, however, our man of the match goes to Crusaders flank Matt Todd. The No.7 work hard around the fringes and managed to steal the ball at the crucial moment.
Tries: Hall, Dagg, Tamanivalu 2
Cons: Mo'unga 2
Pens: McKenzie 2
Crusaders: 15 David Havili, 14 Israel Dagg, 13 Jack Goodhue, 12 Ryan Crotty, 11 Seta Tamanivalu, 10 Richie Mo'unga, 9 Bryn Hall, 8 Kieran Read, 7 Matt Todd, 6 Jordan Taufua, 5 Samuel Whitelock (captain), 4 Scott Barrett, 3 Owen Franks, 2 Codie Taylor, 1 Joe Moody.
Replacements: 16 Ben Funnell, 17 Wyatt Crockett, 18 Michael Alaalatoa, 19 Luke Romano, 20 Pete Samu, 21 Mitchell Drummond, 22 Mitchell Hunt, 23 George Bridge.
Chiefs: 15 Damian McKenzie, 14 Tim Nanai-Williams, 13 Anton Lienert-Brown, 12 Charlie Ngatai, 11 James Lowe, 10 Aaron Cruden (co-captain), 9 Tawera Kerr-Barlow, 8 Michael Leitch, 7 Sam Cane (co-captain), 6 Liam Messam, 5 Brodie Retallick, 4 Mitchell Brown, 3 Nepo Laulala, 2 Nathan Harris, 1 Kane Hames.
Replacements: 16 Liam Polwart, 17 Aidan Ross, 18 Atu Moli, 19 Dominic Bird, 20 Lachlan Boshier, 21 Finlay Christie, 22 Stephen Donald, 23 Shaun Stevenson.
Referee: Glen Jackson (New Zealand)
Assistant referees: Angus Gardner (Australia), Ben O'Keeffe (New Zealand)
TMO: Glenn Newman (New Zealand)