Leinster advanced to their first Champions Cup final since 2012 after swatting Scarlets aside in an utterly dominant 38-16 win at the Aviva Stadium.
Leo Cullen's men were relentless as they put the Welsh region to the sword, notching first-half tries through James Ryan, Cian Healy and Fergus McFadden, and adding two more after the break from man-of-the-match Scott Fardy and Jonathan Sexton.
They had clearly done their homework after last year's Guinness Pro12 semi-final defeat to Scarlets, McFadden's try on the stroke of half-time giving the Irish province a 24-9 half-time lead.
Leigh Halfpenny's three penalties from three attempts, and a slight scrum advantage, were Scarlets' only positives in this one-sided Celtic clash, and they salvaged some pride late on with a try from their former Leinster forward Tadhg Beirne.
It was Leinster's eighth straight European victory this season and sets up the possibility of an all-Irish final in Bilbao in three weeks' time if Munster can come through Sunday's semi-final against Racing 92.
Beirne forced an early turnover to lift Scarlets, who had reached the last four for the first time since 2007. Steff Evans then drew a high tackle from Fardy which allowed Halfpenny to smash over a sixth-minute penalty for the lead.
That brought the best out of Leinster, Rob Kearney finding a superb touch and Fardy charging down Aled Davies, before they went wide and Ryan evaded Beirne's attempted tackle and bounced up to score his first try for the province, converted by Sexton.
The hosts were 10-3 in front after fit-again centre Robbie Henshaw had a couple of powerful runs and Scarlets infringed close to the posts, allowing Sexton to widen the margin to seven.
Halfpenny's supreme goal-kicking kept the Welshmen within range, despite the concession of a second Leinster try.
A scrum penalty against Healy closed the gap to 10-6 before the Ireland prop, with support from the ever-wlling Fardy, crashed over for a 26th-minute converted score. Sexton's initial cross-field kick had seen Steff Evans concede a five-metre scrum.
Halfpenny punished a Daniel Leavy offside seven minutes later, but Leinster's forwards flooded forward from a late penalty and the pressure told, Garry Ringrose flinging a pass wide for winger McFadden to reach over in the right corner ahead of Steff Evans.
Sexton added the conversion for good measure, putting 15 points between the sides at the interval, and Leinster showed no signs of letting up when play resumed.
Tadhg Furlong lost the ball in contact as Scarlets defended close to their line, a Sean Cronin break had Leinster knocking on the door again with Jordan Larmour, a replacement for the injured McFadden, showing his sidestepping ability.
It was Larmour who ripped the ball from Rhys Patchell to set the wheels in motion for the fourth try, Ryan and Fardy combining slickly in the 22 for the Australian international to power over. Sexton's conversion made it 31-9.
Leinster's pack came hunting for more, carrying hard on the hour mark before Sexton stepped off his left foot for a smart finish. In contrast, Scarlets knocked on from a gilt-edged lineout opportunity, and they needed Scott Williams' last-ditch tackle to deny Kearney a try.
With their strong bench keeping them on the front foot, Leinster missed out on a further try when a lunging Fardy had a 73rd-minute score chalked off for hands in the ruck.
The former Wallaby missed a tackle which allowed Beirne through for his consolation score, with Patchell drop-kicking the conversion.