Risca booked their place in the semi-finals of the SWALEC Plate after ending Cardiff University's cup dream with a thrilling 48-28 victory.
Risca are now the lowest-ranked side left in the competition, but will surely fancy their chances after a stunning eight try haul.
Tries from Rhys Putter and Rhys Carpenter and David Jefferson helped the home side on their way to a 26-14 half-time lead, but it was in the second period that Risca really turned on the style.
Two tries from number 8 Richard Evans and a try each from Nicky Davies, Owen Cooper and Tim Barnes completed the rout, although the students of Cardiff went down fighting and can be proud of their displays in this season's competition.
Tredegar Ironsides pulled off the shock of the day with a 15-0 win over Nantyffyllon. The Division Four East outfit grabbed a try in each half through wing Lewis Pritheroe and centre Craig Monaghan.
Rhydefelin survived a second-half comeback from fellow Division Two East side Mountain Ash to win 21-15 at Parc Duffryn Pennar.
The away side had lead 15-5 at half-time thanks to two tries from Aled Jones, before tries from centre Adrian Owen and Dale Keppin hauled Mountain Ash back into the game.
Two penalties from Geraint Watts kept the home side at bay to ensure Rhydyfelin's passage into the final four.
In the remaining quarter-final game Ammanford ran in three tries as they beat Newcastle Emlyn 28-15.
Meet the members of the WRU's inaugural Youth Board - after an online selection process which saw a host of high calibre candidates submit video applications the WRU has made its first 15 appointments.The board is made up of individuals aged between 16 and 21, and will meet for the first time at Principality Stadium on Monday 15th February.
The Wales Women's team headed to Dare Valley Country Park on a team bonding exercise as the entire squad got together for the very first time in preparation for this season's Six Nations championship which kicks off on Saturday with a clash against defending champions Ireland, in Donnybrook.
Wales Head Coach Warren Gatland discusses his team selection for the opening round of the RBS 6 Nations where he leads his side against Ireland, on Sunday. As WRU TV's Luke Brodley discovers, Gatland is fully aware of the challenges the defending champions pose