Gloucester were starting on the road that, they hoped, would lead to a third time lucky appearance in the cup final.
The Cherry and Whites were runners-up in the last two finals, going down 30-24 to Northampton last March at Worcester's Sixways which followed a 50-point thrashing in 2009 at Twickenham by Cardiff Blues.
The Dragons, meanwhile, had hardly set the tournament alight in their few years of participation.
However, buoyed by a surprise but welcome debut victory over the Ospreys at Swansea's Liberty Stadium last weekend, the home side took first blood against a Cherry and Whites' outfit brimming with international players.
With Gloucester pressurising on the Dragons' 22, wing Aled Brew, released for the game from the Welsh Autumn Test squad, created the opening points with a superb kick downfield.
He followed that up by getting off the floor to tackle full-back Olly Morgan, yielding a richly deserved penalty for the wing which fly-half Matthew Jones landed.
Jones booted the Dragons into a six-point lead soon after but, with Gloucester's powerhouse pack led by former Newport favourite Peter Buxton, causing the home side problems in the set-pieces, the platform was there for the visitors to dominate.
Yet, the Dragons grabbed the first try - and it was a cracker.
As the Cherry and Whites attacked through midfield, somehow the Welshmen turned them over.
And from 70 metres full-back Pat Leach stormed down the right touchline to link with wing Adam Hughes, who stormed over near the posts - making Jones' conversion simple.
That forward dominance by Gloucester, whose mighty front row of Scottish prop Alasdair Dickinson, France cap Olivier Azam and former Brive tight-head Pierre Capdevielle dominated their opposite numbers, told before half-time.
After three wheeled scrums on the Dragons' line, referee James Jones decided the home team were deliberately preventing a pushover try and awarded a penalty try which fly-half Freddie Burns easily converted.
The teams faced drizzle which made handling difficult but, with all credit, they both tried to play some decent rugby in the conditions.
England wing Lesley Vainikolo went over in the right hand corner during the second half and the writing seemed to be on the wall.
But the Dragons held on to their slender one-point lead for another 20 minutes and eventually got a rolling maul try when they pushed the visiting eight back over their own line, with flanker Robin Sowden-Taylor getting the congratulations from his team-mates.
Then came the Gloucester onslaught in injury time but the brave Welshmen would not yield and came through to hold out and win.
Final Score Dragons 18 (13) Gloucester 12 (7)
Tries: Hughes, Sowden-Taylor
Penalties: Jones 2
Tries: Penalty, Vainikolo
Gloucester Rugby:Olly Morgan; Tom Voyce, Henry Trinder, Jonny May, Lesley Vainikolo; Freddie Burns, Jordi Pasqualin; Alasdair Dickinson, Olivier Azam, Pierre Capdevielle; Dan Williams, Alex Brown; Peter Buxton (capt), Akapusi Qera, Matt Cox
Replacements:Darren Dawidiuk, Yann Thomas, Rupert Harden, Jim Hamilton, Luke Narraway, Rory Lawson, Tim Taylor, Charlie Sharples
Dragons : Pat Leach, Adam Hughes, Rhodri Gomer-Davies, Ashley Smith, Aled Brew, Matthew Jones; James Leadbeater; Hugh Gustafson, Tom Willis (C), Pat Palmer, Adam Jones, Scott Morgan, Lewis Evans, Robin Sowden-Taylor, Hugo Ellis