On a night when Latrell Mitchell sent a warning to the competition and David Fifita starred, the Rabbitohs hit their first half-century of the year against a Roosters side resting nine stars.
The result means Souths will almost certainly finish sixth and play Newcastle next weekend in an elimination final at either Allianz or Accor stadiums.
The Roosters are locked into fourth and will travel to face whoever claims the minor premiership out of the Warriors or Penrith.
South Sydney's history is littered with emotion, not least of which the club's NRL exile in 2000 and 2001, before their 2002 return.
But no season has carried this much feeling, from Alex Johnston breaking the try-scoring record and Nathan Merritt's cancer battle, to Arrow's motor neurone disease diagnosis.
Arrow has been central to the Rabbitohs' story since his announcement in May, with fundraisers in June and July preceding two brief returns over the past week.
A sold-out crowd rose for Arrow on Friday as he brought up his 100th Rabbitohs game, before he walked off ahead of kick-off for a long embrace with Wayne Bennett.
Asked if it was the most emotional moment he had been part of in 50 years of coaching, Bennett replied: "Probably".
"I've had some pretty tough moments with other players for other reasons. But this was nice," he said.
Souths have won all four of the matches set up to honour Arrow this year, with that no doubt a driving factor for finals.
Friday night was also a near-perfect warm-up.
After playing 30 minutes last week in his first game since round 11, Mitchell showed signs of his damaging best at left centre for the Rabbitohs.
Three times he put Johnston into space, once resulting in a try for the winger as part of a classic left-edge Rabbitohs movement that also included Cody Walker.
Mitchell also scored late and put a monster hit on rookie half Toby Rodwell, while Walker bagged a try of his own in the second half.
Both Bennett and captain Cameron Murray admitted afterwards they were nervous Mitchell could find himself in trouble for the hit, before replays cleared it.
"He needed to get some time behind him tonight and get involved in the game," Bennett said.
"I took a risk; I could have played him less time... But he was enjoying himself and wasn't under stress out there in that second half.
"He had that bit of a swagger that he has back, and he did some really good things. So I was really pleased with the outcome."
Fifita was also at his powerful best, getting the Rabbitohs' first from dummy-half and finishing the night with 11 tackle busts, while Campbell Graham bagged a double.
The only downside for the Rabbitohs was Euan Aitken ending the night in a sling with a shoulder injury, after waiting 201 games to play another final after last doing so in 2015.
The Roosters weren't short on emotion either on Friday, with Spencer Leniu baiting Rabbitohs fans while coming off the field in the first half.
Leniu had just twice clashed with Keaon Koloamatangi in the space of a minute, giving away a penalty in possession after initially earning a set restart.
The Roosters prop was not brought back on by coach Trent Robinson, while Lachlan Hubner and De La Salle Va'a were sin-binned after another melee late.
"I loved the fire from Spenny," Robinson said.
"We spoke about that (penalty) and I'll encourage him to be himself and take on the opposition.Â
"And then he has enough experience that he should have regulated that and just played the ball."
Winger Daniel Tupou got through his return from a shoulder injury unscathed and scored an early try, while the Roosters youngsters turned it on briefly in the second half.
A Cody Ramsey flick pass helped send Rex Bassingthwaighte over for the first of his two tries, before Benaiah Ioelu and a rampaging Taylor Losalu put Egan Butcher over.
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