We look at all the Friday matches
Defending champions Leinster made a winning start to their Pro12 campaign.
Jimmy Gopperth, signed from newly promoted Premiership club the Newcastle Falcons, showed he is capable of filling Jonny Sexton's boots in the 42-19 bonus-point victory over the Scarlets.
In other First Round action on Friday Jason Tovey enjoyed a fine return to the Newport Gwent Dragons, kicking all the points in a 15-8 victory over Ulster to ensure Lyn Jones' tenure got off to a fine start.
The last match of the day saw Tommy Seymour score the crucial try as Glasgow Warriors got their Pro12 campaign off the ground with a hard-fought 22-15 win over Cardiff Blues.
We look at all Friday's matches!
Glasgow Warriors 22-15 Cardiff Blues
Tommy Seymour scored the crucial try as Glasgow Warriors got their Pro12 campaign off the ground with a hard-fought 22-15 win over Cardiff Blues.
Seymour struck with 12 minutes left on the clock and with his side in trouble at 15-12 down, thanks to four penalties and a drop goal from Blues fly-half Rhys Patchell.
But in the end, last season's semi-finalists ground out the victory in the torrential rain despite some late Blues pressure.
The Warriors, on the back of a seven game winning streak at Scotstoun, drew first blood in the opening stages when the Blues were penalised for going over the top - Scott Wight striking a fine penalty to give the hosts a 3-0 lead.
Just three minutes later however, the Blues were level when the Warriors were pinged for crossing and fly-half Patchell, who made his Wales debut over the off-season in Japan, levelled things up from the tee.
That gave the Blues a boost and only desperate scrambled defence from the home side, behind their own try line, denied the visitors a score.
The Blues came again however and when Warriors flanker Chris Fusaro was adjudged offside, Patchell made a mockery of the treacherous conditions with his second penalty of the night on nine minutes.
There was little to separate the two sides in the opening exchanges however and the Warriors restored parity soon after, Mark Bennett temporarily taking over kicking duties to make it 6-6.
Patchell then missed the target with another penalty before the hosts were forced into two changes through injury - Jonny Gray replacing Al Kellock and Tommy Seymour coming on in place of Byron McGuigan.
But it was the Warriors who regrouped and took the lead again, Wight on target, having retaken the kicking duties, after Blues centre Owen Williams was shown a yellow card for a deliberate trip.
Wight had another chance to double his side's advantage soon after when Blues No.8 Robin Copeland was offside but he was wayward - but Bennett stepped up again just before half-time to give the home side a six-point lead at the break.
The conditions were unrelenting and weren't making for running rugby but the Blues clawed their way back into the match - Patchell trimming the gap to three with his third penalty of the night.
He had another chance soon after from just inside his own half and didn't quite have the range but Patchell made amends on 55 minutes to level the scores at 12-12.
Just after the hour mark, Bennett stepped up to the tee after Williams was penalised for not rolling away but could land his kick and Patchell handed the Blues the lead on 66 minutes with a fine right-footed drop goal.
But Glasgow then got the decisive score with Seymour picking the ball up off his toes before breaking the Blues line and romping over in the right-hand corner.
Another replacement Ruaridh Jackson nailed the conversion from the touchline to give the Warriors a 19-15 lead and he added a penalty soon after following Macauley Cook's yellow card.
But back came Cardiff and they thought they had forced their way over the line, only for the referee to rule out the try but send Warriors' Richie Vernon to the sin bin.
The Blues had two scrums just short of the Warriors' line but they could find no way through as the hosts held on for the victory.
For Glasgow Warriors:
Pens: Wight 2, Bennett 2, Jackson
For Cardiff Blues:
Pens: Patchell 4
Glasgow Warriors: 15 Peter Murchie, 14 Sean Lamont, 13 Mark Bennett, 12 Alex Dunbar, 11 Byron McGuigan, 10 Scott Wight, 9 Henry Pyrgos, 8 Richie Vernon, 7 Chris Fusaro, 6 Rob Harley, 5 Al Kellock (captain), 4 Tim Swinson, 3 Ed Kalman, 2 Pat MacArthur, 1 Jerry Yanuyanutawa.
Replacements: 16 Fraser Brown, 17 Gordon Reid, 18 Moray Low, 19 Tyrone Holmes, 20 Jonny Gray, 21 Chris Cusiter, 22 Ruaridh Jackson, 23 Tommy Seymour.
Cardiff Blues: 15 Tom Williams, 14 Harry Robinson, 13 Owen Williams, 12 Gavin Evans, 11 Chris Czekaj, 10 Rhys Patchell, 9 Lloyd Williams, 8 Robin Copeland, 7 Josh Navidi, 6 Macauley Cook, 5 Filo Paulo, 4 Bradley Davies, 3 Scott Andrews, 2 Matthew Rees (captain), 1 Taufa'ao Filise.
Replacements: 16 Marc Breeze, 17 Sam Hobbs, 18 Benoit Bourrust, 19 James Down, 20 Luke Hamilton, 21 Lewis Jones, 22 Gareth Davies, 23 Dafydd Hewitt.
Referee: Dudley Phillips (Ireland)
Assistant referees: David Changleng (Scotland), Graeme Marshall (Scotland)
TMO: Jim Yuille (Scotland)
Newport Gwent Dragons 15-8 Ulster
Jason Tovey enjoyed a fine return to the Newport Gwent Dragons, kicking all the points in a 15-8 victory over Ulster to ensure Lyn Jones' tenure got off to a fine start.
The Dragons limped into 11th place last season but in came Jones over the off-season and he has already made a difference - the Welsh outfit seeing off last season's Pro12 runners-up.
Ulster scored the only try of the match through Roger Wilson but they were lacklustre for large spells, where as the Dragons were resolute and were fortunate that Paddy Jackson's radar was off target.
Eager to impress their new coach, the Dragons began brightly with both young winger Hallam Amos and No.8 Lewis Evans making surging runs early on.
Fly-half Tovey, who spent last season at Cardiff Blues, missed his first penalty on his second debut for the Dragons but he made no mistake with an expert drop goal soon after to give the hosts a ninth-minute lead.
Ulster gradually grew into the game however and last year's Pro12 regular season table toppers were level on 13 minutes thanks to a Jackson penalty after the visitors exerted their dominance at the scrum.
The Dragons maintained their early momentum however and retook the lead on 15 minutes after Ulster prop Callum Black was pinged for holding on - Tovey this time hitting the target.
Just three minutes later however Ulster had their first try of the season - expertly worked after opting to kick for a lineout rather than for the posts and from the subsequent set-piece, the visitors formed a rolling maul and No.8 Watson trucked the ball up to the line and dived over.
Jackson missed the conversion however - a sign of things to come - and he did so again five minutes later with three points on offer, both times erring to the right.
Yet again Jackson could not find his range and on 34 minutes he let the Dragons off the hook, only for Tovey to follow suit from the right-hand touchline with three minutes left in the half.
Ulster flew out of the blocks in the second half but gave away a penalty with the tryline beckoning as the Dragons ensured they stayed within touching distance.
And they took the lead on 49 minutes when Tovey found his kicking boots again after Ulster captain Johann Muller was penalised at the breakdown.
Back came Ulster however with a fine length-of-the-pitch move, started by Wilson and after moving the ball to the right, Chris Farrell's chip over the top was just too long for Andrew Trimble.
On the hour mark, Tovey further extended the home side's lead after Ulster infringed at the scrum, the left-footer nailing a fine effort to give his side a four-point cushion.
Despite their deficit, Ulster failed to trouble the Dragons and with nine minutes to go, Tovey struck his fourth penalty of the night to put his side 15-8 to the good.
That stirred Ulster into life and they spent a sustained period of time camped on the Dragons line but the hosts defended superbly to withstand the pressure and while Tovey missed a late drop goal effort, it wasn't to matter as Jones' men held on for the victory.
For Newport Gwent Dragons:
Pens: Tovey 4
Newport Gwent Dragons: 15 Dan Evans, 14 Tom Prydie, 13 Pat Leach, 12 Jack Dixon, 11 Hallam Amos, 10 Jason Tovey, 9 Richie Rees, 8 Lewis Evans, 7 Nic Cudd, 6 Jevon Groves, 5 Andrew Coombs (captain), 4 Matthew Screech, 3 Dan Way, 2 Thomas Rhys Thomas, 1 Aaron Coundley.
Replacements: 16 Hugh Gustafson, 17 Phil Price, 18 Francisco Chaparro, 19 Adam Jones, 20 Netani Talei, 21 Jonathan Evans, 22 Kris Burton, 23 Ross Wardle.
Ulster: 15 Jared Payne, 14 Andrew Trimble, 13 Luke Marshall, 12 Chris Farrell, 11 David McIlwaine, 10 Paddy Jackson, 9 Paul Marshall, 8 Roger Wilson, 7 Chris Henry, 6 Robbie Diack, 5 Dan Tuohy, 4 Johann Muller (captain), 3 Ricky Lutton, 2 Rob Herring, 1 Callum Black.
Replacements: 16 Niall Annett, 17 Tom Court, 18 Declan Fitzpatrick, 19 Lewis Stevenson, 20 Sean Doyle, 21 Ian Porter, 22 James McKinney, 23 Darren Cave.
Referee: Claudio Blessano (Italy)
Assistant referees: Leighton Hodges (Wales), Neil Hennessy (Wales)
Scarlets 19-42 Leinster
Defending champions Leinster made a winning start to their Pro12 campaign as Jimmy Gopperth showed he is capable of filling Jonny Sexton's boots in the 42-19 bonus-point victory over the Scarlets.
Gopperth joined from English side Newcastle Falcons in the off-season while Sexton moved to Racing Metro in France but the new arrival looked comfortable in the No.10 shirt, kicking 17 points.
The 30-year-old also ran in his side's fourth try of the night as Leinster overturned a 16-10 deficit at the break to taste victory in the opening round for just the second time since 2003.
Scarlets had won four of their past five opening home fixtures and began in fine style when Aaron Shingler burst through Leinster's defensive lines and brother Steven Shingler slotted the penalty that followed.
Steven Shingler, who returned from London Irish this off-season, doubled the advantage with another penalty after Dave Kearney was sin-binned for a high tackle on Scott Williams, who had made a superb break and looked destined for the corner.
Aaron Shingler continued to shine in the Scarlets' back-row and another fine break, followed by a forwards drive, saw captain Rob McCusker dive under the posts, with Steven Shingler converting.
Defending champions Leinster have a rotten record in the opening round of the competition but they were back in the contest after a fine lineout and drive resulted in prop Martin Moore crossing the whitewash.
Summer signing Gopperth made no mistake with the conversion to make it 13-7 and then added another penalty but Steven Shingler hit back with one of his own to send Scarlets in 16-10 up at the break.
Brendan Macken sparked Leinster into life as soon as the second-half began, beating two tacklers before off-loading for Jordi Murphy to score with Gopperth slotting the conversion to put the Irish side 17-16 ahead.
Gopperth then added a further penalty as Leinster attempted to pull clear but they were reduced to 14 men when replacement Darren Hudson was sent to the sin bin for a high challenge on Liam Williams.
The Scarlets duly capitalised when Steven Shingler was again successful from the kicking tee but on 62 minutes Gopperth restored Leinster's four-point cushion when he kicked another penalty.
Leinster looked to have made the game safe when a great move allowed prop Jack McGrath to off-load the ball to the Hudson, back from the sin bin, to cross for the try.
And any doubt was removed when Gopperth claimed the try his performance deserved as he collected an inside pass from Devin Toner to grab the bonus-point score and Kearney had the last word to take Leinster to 40 points.
Pen: Shingler 4
Tries: Moore, Murphy, Hudson, Gopperth, Kearney
Con: Gopperth 4
Pen: Gopperth 3
Scarlets: 15 Gareth Owen, 14 Liam Williams, 13 Scott Williams, 12 Steve Shingler, 11 Kristian Phillips, 10 Rhys Priestland, 9 Gareth Davies, 8 Rob McCusker (captain), 7 Josh Turnbull, 6 Aaron Shingler, 5 Jo Snyman, 4 George Earle, 3 Samson Lee, 2 Ken Owens, 1 Phil John.
Replacements: 16 Emyr Phillips, 17 Rob Evans, 18 Jacobie Adriaanse, 19 Jake Ball, 20 Craig Price, 21 Rhodri Williams, 22 Adam Warren, 23 Jordan Williams.
Leinster: 15 Dave Kearney, 14 Darragh Fanning, 13 Fergus McFadden, 12 Gordon D'Arcy, 11 Luke Fitzgerald, 10 Jimmy Gopperth, 9 Eoin Reddan, 8 Jordi Murphy, 7 Shane Jennings (captain), 6 Rhys Ruddock, 5 Devin Toner, 4 Tom Denton, 3 Martin Moore, 2 Sean Cronin, 1 Jack McGrath.
Replacements: 16 Aaron Dundon, 17 Jack O'Connell, 18 Mike Ross, 19 Mike McCarthy, 20 Dominic Ryan, 21 Isaac Boss, 22 Noel Reid, 23 Brendan Macken.
Referee: John Lacey (Ireland)
Assistant referees: Ian Davies (Wales), Jon Mason (Wales)
TMO: Derek Bevan (Wales)