The Dragons led 48-0 early in the second half to inflict the biggest score on the Ospreys in the region’s history.
Yet somehow the Ospreys mustered remarkable recovery that left the Dragons with 13 men and hint at a sensational comeback.
Lewis Evans celebrated his 150th appearance for the Dragons with two tries in a devastating display by the Dragons pack after Ross Wardle’s opener on eight minutes.
Evans reaped the rewards of the experienced front-five who masterminded three successive lineout drives, the second from 35 metres finished by Cory Hill, to march into a 34-0 lead.
The pressure saw Ospreys lock Rory Thornton binned before Jonathan Evans and Hill, for his second, score either side of half-time.
By the time Hanno Dirksen crossed in the 49th minute, the Dragons were already 48-0 ahead and the result an apparent formality.
Yet Dirksen sparked a remarkable response as the Ospreys hit back with five second-half tries of their own. Dafydd Howells and Cai Griffiths followed before the tables were turned on the Dragons pack as the Ospreys earned a penalty try.
The card for Dorian Jones, who had kicked 21 points, just a minute after lock Joseph Davies left Dragons with 13 men and wing Aisea Natoga took full advantage.
The Brewery Field held its breath to see if the Ospreys could complete a sensational comeback but the Dragons held out, but only just.
