Penrith's multimillion-dollar punt on the Clearys has marched them into their first grand final in 17 years, with Nathan kicking them clear of Souths on the paddock and Ivan matching wits with Wayne Bennett off it.
The 20-16 triumph at ANZ Stadium was as thrilling as it was ugly, Penrith bombing the best part of half-a-dozen scoring opportunities against a busted Bunnies outfit.
Regardless, the four-point triumph sets up a date with Melbourne next Sunday with a crack at crowning one of the most successful seasons in history against the most prolific club of the NRL era.
As the Rabbitohs kept coming Penrith's Chocolate Soldiers nearly melted under the pressure - Api Koroisau's brief exit on the hour mark with a "stinger" to his shoulder having hearts in mouths from Blacktown to Mt Druitt.
In turn Ivan Cleary's surprise call to put back-up rake Mitch Kenny on his bench proved a shrewd move, so too his plumping for Tyrone May at centre over Brent Naden.
Match: Panthers v Rabbitohs
Finals Week 3 -
Venue: Accor Stadium, Sydney
Son Nathan's million-dollar boot gave Penrith the ascendancy in a clunky first half, with two tries laid on before a Rabbitohs resurgence after the break brought the Panthers' nerves to the fore.
With Bayley Sironen (knee) out for the game and Corey Allan walking wounded, the Rabbitohs still threatened to run the Panthers down.
A 14-6 half-time lead disintegrated before the Panthers' eyes as they bombed several second-half scoring opportunities.
Yeo busts the Bunnies to provide for Edwards
Just as a cardinal and myrtle upset loomed, Isaah Yeo busted up the middle with the type of run that has him in line for a NSW Origin call-up, Dylan Edwards's four-pointer in support providing much-needed breathing space on the road to a 17th straight victory.
With eight minutes remaining the Rabbitohs faithful drowned that out.
Despite carrying a significant cork that had him operating at little more than a limp, Allan's effort was Herculean as he grubbered ahead a Cody Walker pass and dotted it for a thrilling finish.
But for Adam Reynolds' toes being four centimetres the wrong side of a critical 40-20 with three minutes to play, Penrith's stunning match streak could easily have come to an end.
Penrith clung on but if they are to make it 18 in a row at the same venue next week they will need their form from the rest of 2020, and not this error-riddled 80 minutes, to compete with a Storm outfit in their 10th grand final from 23 seasons.
Cleary explains his reasoning for starting May
"We left a lot of points out there in the first half,'' coach Ivan Cleary said afterwards.
"We started really well, apart from conceding the first try, but we did a lot of things right and looked dangerous. We had a lot of running in the legs.
"We turned over too much possession throughout the night to keep them in the game. We could have scored another three tries in the first half.
Johnston spills the Cleary kick and To'o benefits
"We had a lot of tired boys out there, young guys who haven't been through that pressure, so it was a great preparation for next week."
From the outset nervous moments abounded for Penrith, starting with a stumbling charge-down attempt from skipper James Tamou in the first minute.
Reynolds sprayed the early penalty shot at goal but when he went to the boot again the missed two points became a spectacular six.
Kicking on the first tackle after Allan stripped the Steeden from Edwards, Reynolds put it on a dime for Alex Johnston to cash in with a simple take on Penrith's try-line.
Cleary takes his turn at dropping pin-point kicks
Within minutes Brian To'o was crossing for a square-up from Johnston's own fumble flying through the air, Cleary with the nudge for a 6-6 game.
The score hadn't changed by the 17th minute but both sides had already burned their captain's challenges with ill-advised efforts.
Up the middle and down the left edge Penrith began to split the Rabbitohs defence, targeting Campbell Graham's right centre replacement Jed Cartwright with fortune and then some.
An inexplicable forward pass from Josh Mansour to Kurt Capewell with a try on offer kept South Sydney level.
A high shot from James Fisher-Harris on Tevita Tatola then landed the Kiwi enforcer on report and gave the Rabbitohs yet more relief.
It proved fleeting though as Penrith's momentum piled up, Cleary once more putting boot to ball and this time his housemate May latched on for a 12-6 lead.
Another pin-point Cleary kick saw Cartwright take out a Panthers chaser, the mercurial No.7 knocking over the penalty for 14-6 at the break.
A botched try from centre Stephen Crichton, fluffing another Cleary chip that sat up for him in the in-goal, kept the Bunnies in it.
So too Johnston's determined grassing of Crichton when he was en route to the line with one of 2020's finer try-saving tackles, Dane Gagai’s 49th minute try dragging them ever closer.
So the second half went, Penrith pushing, South Sydney pushing back and clutch plays abounding.
In the end, the Panthers' resilience and Cleary's brilliance proved just enough to get them home.