Reigning champions Glasgow Warriors were knocked out in the semi-finals last weekend as Ulster also fell by the wayside.
With both home sides winning their respective semi-finals it continued the 100 per cent record of the regular season's top two sides contesting the Grand Final.
Who will win the Guinness PRO12 trophy is yet to be seen, but the route to the final has not been straight forward.
The Early Winners:
The Guinness PRO12 began in advance of the 2015 World Cup, and it began with a bang.
Cardiff Blues laid down a marker to the rest of the league on the opening day, running in 11 tries in a 48-point victory over Zebre.
The usual suspects struggled on the opening weekend though as Leinster were downed 16-9 in Edinburgh and reigning champions Glasgow Warriors succumbed at home to Scarlets.
That victory was just the start for Scarlets as the Welsh region won all six of their opening games, the highlight being a Round 4 win over Leinster.
Connacht began in fine fettle too, Pat Lam's men beat Newport Gwent Dragons on opening day before losing by the odd point in 55 at Glasgow Warriors in Round 2.
After that though the Galway men went on a six-game winning run to make it seven wins from their opening eight games and saw them sitting pretty atop the Guinness PRO12 table.
The run-in:
At the mid-way point of the season Glasgow Warriors were in danger of ending their defence without even making the semi-finals.
Gregor Townsend's men kicked into life in Round 15 though and went on a nine-game winning run and even topped the table heading into the final round of games.
Fly-half Finn Russell was on fire and his star shone brightest in Round 20 as he inspired Warriors to a 46-10 win over Scarlets in Wales, scoring two tries along the way.
Connacht had led for the majority of the season but stumbled in the closing rounds and went into the final day placed third in the league.
Leinster's up and down spring was epitomised by a single-point loss to leaders Connacht in Round 18 before beating fierce rivals Munster in Round 19 to take advantage of the Galway men's loss and leapfrog them at the top of the table.
Heading into the final round Glasgow led the way, Leinster were second, Connacht third and Ulster fourth.
Leinster ran in eight tries to beat Treviso 50-19 and Ulster scored six of their own to win 46-26 in Swansea against the Ospreys.
Those wins confirmed semi-final spots for the victors with Ulster cementing their fourth place, but the order of the top three would be decided by the outcome of Connacht against Warriors.
Lam's side, leaders for so much of the season, would not miss out on a home semi-final as they won another tight affair 14-7, Townsend's men slipping from first to third in the table.
At the foot of the table Zebre overtook Treviso to secure the Italian spot in next season's Champions Cup while Scarlets and Munster finished fifth and sixth to join the Parma side, and the top four, in Europe's elite competition.
Blues finished seventh with Ospreys eighth, and Dragons tenth, to complete a disappointing season for the Welsh regions.
The play-offs:
With the top three separated by just one point in the end-of-season table, was this going to be the year for an away semi-finalist to upset the apple cart and book a spot in the Grand Final?
No.
The first semi-final went according to the script as Leinster, who finished four points ahead of their inter-provincial rivals Ulster in the table, showed their play-off pedigree with a 30-18 win at the RDS.
Isa Nacewa got the home side off to a flying start with a fourth minute try before Jonathan Sexton kicked the Boys in Blue into a 13-point lead with just 15 minutes played.
Paddy Jackson kept the Ulstermen in touch though before a Craig Gilroy try cut the Leinster lead even further.
Jamie Heaslip and Sean Cronin crossed the whitewash to calm Leo Cullen's nerves though, meaning Gilroy's second try was in vain and Leinster made their sixth final in seven years.
The second semi-final was a much tighter affair, in scoreline at least.
Warriors lost their fly-half Finn Russell to injury after just 69 seconds and Niyi Adeolokun's try gave the home side a deserved half-time lead.
Glasgow's departing lock, Leone Nakarawa, touched down early in the second period but AJ MacGinty's trusty boot did enough to kick Pat Lam's men to a maiden Celtic League final as Connacht finished 16-11 winners.
Top Scorers:
There are new names atop the leading scorer tables this season, but will Gilroy hang on to take the leading try scorer crown?
The Ulster back crossed the whitewash ten times this season but Connacht's Matt Healy and Isa Nacewa, of Leinster, are just one try behind him and ready to pounce with a match-winning contribution in the Grand Final.
Rhys Patchell cannot be caught atop the top scoring table though, the Cardiff Blues full-back being 19 points ahead of his nearest rival.
With 174 points, Scarlets-bound Patchell has led the standings for the majority of the season with Benetton Treviso's Jayden Hayward and Sam Davies, of Ospreys, his closest competition with 155 and 152 points respectively.
With no Connacht or Leinster players close to Patchell's tally, he is certain to finish the season as top-scorer.
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