Hosts Cardiff Blues and Newport Gwent Dragons became the first-ever Welsh teams to qualify for the Premiership Rugby 7s Series Final after an impressive display of pace and power at Arms Park.
Both regions beat Scarlets and Ospreys and in the final match of the night, the Blues drew with the Dragons 19-19 - through a penalty try - to emerge as group victors on bonus points. They will now travel to the Twickenham Stoop on 8 August for the Series Final.
However, the Blues received a painful wake-up call to start the night - in their opener against the Ospreys - as Steff Andrews first charged over - after fine work from Chris Williams - before Wales 7s international Ross Jones made it two.
But Tomos Williams pulled one back before Owen Jenkins shimmed his way through to level the scores at 14-14 going into half-time.
Senior back Dan Fish steamed away to put the Blues in charge for the first time before Aled Summerhill and Ellis Wyn Benham gave them an ample cushion, despite Rob Dudley-Jones' consolation to emerge 33-21 winners.
By contrast the next match was a more sedate affair - but impressive defending and tries from Rhys Jones and Jonny Lewis put Newport Gwent Dragons in the box seat over Scarlets at the interval.
Scarlets responded through Lee Rees and Josh Lewis, but Elliot Frewen jinked his way past three attempted tackles in the last minute to clinch the win for the Dragons.
Matthew Pewtner then ran almost the whole length of the pitch to get the Dragons off to another perfect start against Ospreys, though back-row Morgan Allen showed a neat turn of pace to touch down in reply.
But Oliver Griffiths and Pewtner added second-half scores, before the impressive Frewen and Lewis sped away for tries of their own, to all but seal the Dragons' place at The Stoop with a 33-5 victory.
The Blues then picked up where they left off against Scarlets as experienced trio Fish, Tom Williams and Richard Smith all found joy all secured a 22-7 triumph.
Darran Harris was the man who got on the scoreboard for the Scarlets but nothing was going to stop the Blues from joining the Dragons in the Series Final.
In what was now a third-place consolation match, Scarlets turned on the style in a breathless 61-28 victory over Ospreys.
Scarlets racked up eight tries including Aaron Warren and Lee Rees doubles, while senior wing Kristian Phillips found a well-deserved try in the second half.
Joel Matavesi - brother of former Aviva Premiership wing Josh - touched down for Ospreys, as did Evan Yardley, Ross Jones and Joe Gage, but they could never truly recover from Scarlets' 40-point onslaught in the first half.
And in the final between the group's stand-out two teams, Benham drew first blood for the Blues - but the conversion was missed - as Frewen crossed the whitewash to help Dragons to a 7-5 lead at half time.
Griffiths and Pewtner then added their own contributions as Dragons looked like emerging group winners.
But two tries in the last 90 seconds - through Tom Williams and a penalty try - dramatically saw the Blues top the pile in a 19-19 draw, thanks to their two bonus points to one.
Results: Ospreys 21-33 Cardiff Blues, Newport Gwent Dragons 21-14 Scarlets, Newport Gwent Dragons 33-5 Ospreys, Cardiff Blues 22-7 Scarlets, Ospreys 28-61 Scarlets, Cardiff Blues 19-19 Newport Gwent Dragons
Man of the Round: Matthew Pewtner - Newport Gwent Dragons