Ospreys wing Tommy Bowe makes a break against the Dragons
Ospreys secured home advantage in the Magners League play-offs with a bonus-point win over Newport Gwent Dragons at the Liberty Stadium on Friday.
An injury-hit Dragons limited Ospreys to just a penalty try before half-time, after a series of collapsed scrums.
But the Ospreys cut loose after the restart, with Ryan Jones, Dan Biggar and Nikki Walker all claiming tries.
Glasgow will be Ospreys' opponents in the play-offs, with the semi-final at the Liberty Stadium on Friday, 14 May.
The other semi-final is an all-Irish affair with Leinster at home to Munster, who just held off Cardiff Blues to take fourth spot in the league and the last play-off spot.
Dragons had won their previous encounter with the Ospreys at Rodney Parade in March, but injuries had thinned their ranks for this encounter.
Two early Biggar penalties gave Ospreys the platform to spread the ball, while a pack outweighing the Dragons scrum by nearly a stone a man ensured a steady stream of possession.
Shane Williams came close to claiming the first try but was wrestled into touch by Dragons full-back Will Harries.
Hook delight at home advantage
But the visitors fumbled the resulting line-out to concede a five-metre scrum and the Ospreys turned on the power.
Referee Nigel Owens awarded two penalties as the Dragons desperately tried to disrupt the Ospreys scrum, but after two resets and a third infringement the official's patience ran out and a penalty try resulted.
Alun Wyn Jones gifted Dragons their first points, the Wales and Lions lock first losing the ball in contact and then compounding the error by high-tackling Rhodri Gomer Davies.
Tovey made sure of the penalty kick but Biggar soon restored Ospreys' 13-point lead with his third penalty of the night.
But just a few miles down the road at Parc y Scarlets, Glasgow in their game against the Scarlets had already scored two of the four tries they needed to have a hope of leapfrogging the Ospreys.
So it was tries that the Ospreys desperately needed, although despite much huffing and puffing they were unable to breach the Dragons line again before half-time.
Tommy Bowe almost gave the Ospreys a perfect start to the second half as the Irishman broke down the right wing, only for lock Rob Sidoli to pop up and make a crucial tackle.
Then moments later Lee Byrne just lost control of the ball under a hefty challenge as he dove over the Dragons line.
But the Ospreys kept the pressure on and again had the Dragons on the rack from a five-metre scrum, this time captain Ryan Jones picking up from the base to drop over for a converted try.
To their credit the Dragons refused to buckle and surged upfield, at last able to put the Ospreys line under pressure to send scrum-half Evans over from the base of a ruck.
Yet the Ospreys engineered another five-metre scrum, the creaking Dragons this time losing prop Aaron Coundley to the sin-bin.
It seemed another try would follow, but referee Owens chose to penalise Ospreys prop Adam Jones as the scrum collapsed.
The reprieve was brief, however, as lock Jonathan Thomas caused havoc in the Dragons defence, the front row taking the move on before Biggar went over in the corner.
That all-important fourth try should have followed but Bowe delayed his inside pass to Mike Phillips too long and the ball went forward with the Dragons line in sight.
With 12 minutes remaining the Ospreys finally secured that home advantage as replacement Walker stretched over, the Scotland wing the happy recipient of a great break by Phillips and James Hook's good support.
Replacement prop Ryan Bevington added a rampaging fifth try after Shane Williams had broken through, underlining Ospreys' dominance.
To round off the night for the Ospreys, former New Zealand back-row Filo Tiatia came off the bench for one last run before hanging up his boots to concentrate on his fledgling coaching career.
Ospreys: Lee Byrne; Tommy Bowe, Andrew Bishop, James Hook, Shane Williams; Dan Biggar, Mike Phillips; Paul James, Huw Bennett, Adam Jones, Alun Wyn Jones, Jonathan Thomas, Jerry Collins, Marty Holah, Ryan Jones (capt). Replacements: Ed Shervington for Bennett (73), Ryan Bevington for Adam Jones (65), Ian Gough for Alun Wyn Jones (65), Filo Tiatia for R. Jones (65), Jamie Nutbrown for M. Phillips (73), Gareth Owen for Byrne (66), Nikki Walker for Bishop (66).
Dragons: Will Harries; Adam Hughes, Rhodri Gomer Davies, Pat Leach, Richard Fussell; Jason Tovey, Wayne Evans; Aaron Coundley, Tom Willis, Ben Castle, Robert Sidoli, Hoani MacDonald, Andrew Coombs, James Harris, Lewis Evans. Replacements: Lloyd Burns for L. Evans (41), Pat Palmer for Castle (50), Rhys Jenkins for Harris (75), Jevon Groves for MacDonald (66), Tom Riley for Leach (66), Adam Greendale for Tovey (75), Jonathan Evans for W. Evans (70).
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