Keira and Helensburgh will meet in Illawarra cricket's one-day final after surviving almost terminal batting collapses to win contrasting semi-finals last Saturday.
Minor premiers Keira recovered from 5-27 against Corrimal at North Dalton Park to post 194 and then dismiss the Cougars for 136.
An 84-run sixth-wicket partnership between Jonathon Cook (37) and Neel Honavar (73) turned the match with the Lions lower order aided by 12 bonus runs for a slow over rate by Corrimal.
The Cougars battled hard in the run chase and, despite the loss, had a great return season to first grade.
After a competition-high 754 runs at an average of 94, Lions skipper Graeme Batty made a duck, before striking with the ball, taking 3-30 while Cook (3-19) and Honavar (2-27) also proved damaging.
"Cook and Honavar were fantastic and, as a team, we showed a lot of fight to tough it out and get out of it," Batty said.
"Going through the season unbeaten, then being 5-20 odd in a semi it could have been all over. We've had comebacks before and this was the biggest of them in the biggest game - so far."
Meanwhile, second-placed Helensburgh advanced to meet Keira in Saturday's final after a low-scoring thriller at Figtree Oval.
Just 73.1 overs were bowled with 19 wickets lost for 193 runs.
Having rolled Wollongong for just 96 in 29.2 overs, the Burgh were heading for defeat at 8-69, before wicketkeeper Ryan Morris made a match-winning unbeaten 22.
At 9-91 an anxious Burgh skipper Tim Lloyd strode to the crease with six runs needed for victory.
A Morris single left Lloyd on strike; with the winning runs coming from a wide followed by four leg byes off Lloyd's pads.
"That's the most nervous I've ever been going out to bat," Lloyd said.
"It was nerve-racking to go from a winning position to almost throw it away. Thank heavens for Ryan [Morris]."