Torrential rain led to an error strewn game of few chances, with it then taking a vital try just three minutes from time to draw the home side level and deny the competition defending champs a fourth win of the season.
It also ended the Stormers amazing 14-match winning run, which stretched all the way back to the start of March, which saw them power to last season’s title and then start this season with three bonus point wins.
The Stormers got off to a strong start in the match, dominating possession and territory in the Ospreys half during the first 10 minutes, but some strong defence from the hosts kept the visitors in check.
The Stormers then took a deserved lead in the 13th minute as they earned a scrum penalty between the 10m and 22m, with flyhalf Manie Libbok then slotting the kick for a 3-0 lead.
The Ospreys scrum then started to take charge and they earned their own penalty in the 28th minute, but after choosing to go for the corner instead of posts, ended with the home side losing the ball on attack on the 5m.
From the loose ball the Stormers attacked and were lucky to get away with a forward pass, with them then getting a penalty just short of the halfway for the Ospreys not rolling away.
Libbok lined up the long range kick and duly knocked it over, on the angle from just in his own half to take a 6-0 lead in the 30th minute.
The final 10 minutes then belonged to the home team as they first cut the deficit to three points with a successful penalty from flyhalf Stephen Myler after another dominant scrum from their pack.
They then almost scored the first try of the match in the final minute as they attacked into the Stormers half, got close and then a poor pass from flank Jac Morgan to wing Keelan Giles then saw him knock on with the tryline begging.
The Ospreys then struck first in the second half, earning a penalty just outside the Stormers 22m after holding on at a ruck, with Myler slotting the kick to draw the scores level in the 51st minute.
Four minutes later the Stormers produced their best move of the match, as they attacked from an Ospreys up and under, with the ball from the ruck going to Libbok, who ran a switch with wing Leolin Zas as he hit a gap, got to the 22m and offloaded to scrumhalf Paul de Wet to run in and score.
Libboks extras then put them 13-6 up with 25 minutes to play, but the lead was then cut to four points after another scrum penalty to the Ospreys in the 69th minute allowed Myler to slot his third penalty.
Libbok then restored the seven point lead in the 72nd minute, after the Stormers earned a penalty at a maul on the Ospreys 22m.
With three minutes to go it was all square once again as a couple of penalties allowed the Ospreys to kick into the Stormers 22m, set up a maul and power it over, with replacement hooker Scott Baldwin dotting down, and Myler nailing the difficult conversion from the side.
An audacious drop goal attempt from Libbok on the Ospreys 22m with just 30 second remaining, saw the ball drift wide, with it proving to be the last chance as the game ended in a stalemate.
Ospreys: Try – Scott Baldwin; Conversion – Stephen Myler; Penalties – Myler (3)
Stormers: Try – Paul de Wet; Conversion – Manie Libbok; Penalties – Libbok (3)