The 17-Test Wallabies lock will join the Western Force after seven seasons in Canberra and admits he's desperate to help the Brumbies to a first championship proper in 20 years.
The Brumbies won the domestic 2021 Super Rugby AU crown during COVID-19 but Swain wants the full-blown version, knowing how elusive titles are when New Zealand opposition are involved.
"It would be unreal," Swain said on Monday.
"We haven't done it since '04. There was 2021, but that's a Super AU and it's a bit different.
"That'd be unbelievable to win a Super Rugby title - not many people can do that."
The NSW Waratahs, a decade ago, were the most recent Australian team to claim trans-Tasman supremacy.
The Brumbies take on the Waratahs in Sydney on Saturday night with the chance to hammer another nail in the coffin for their arch-rivals in 2024.
With four regular-season games remaining, time is fast running out for the second-to-last Waratahs to climb into the top eight.
Darren Coleman's side need to win at least two, probably three and maybe all four matches against the Brumbies, Western Force, Moana Pasifika and Queensland Reds to scrape into the finals.
Brumbies centre Len Ikitau expects the Waratahs to be desperate in front of their home fans at Allianz Stadium and says his third-placed outfit can't take the contest lightly despite dominating the rivalry in recent years.
"We treat 'Tah week' as every other week - it's always a tough game," Ikitau said.
"They sure like to turn up when they verse us, so no matter how bad they're going - or good - it's always a tough game against the Tahs."
Best mates Swain and Ikitau went to high school together at Brisbane Boys' College and the lock admits it was a wrench having to tell teammates he was joining the Force.
"It's the toughest decision I've had to make in terms of my future," said Swain, who is expecting his first child next month.
"I had to talk to a lot of people and consider a lot of things but, ultimately, it's my time to move on.
"It happens playing a professional game, it was the opportunity ... to do something different and be part of something different.
"It'll be a good change for me and my family."
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