Frolunda have been beating all comers this season in the Swedish Hockey League (SHL), and facing one of their compatriots in the CHL was always going to provide a psychological boost, and when Brynas' Jakob Silfverberg was sent to the box for slashing after 10 minutes, the away side took advantage.
Linus Hogberg found Ivar Stenberg on the Frolunda left side, and as he cut inside he hammered the puck into the top corner of Erik Kallgren's goal to give the away side the lead on a powerplay.
Four of the next five powerplays would belong to the home side, as Frolunda were twice called for too many men on the ice, but Brynas failed to capitalise, and when they lost Mattias Norlinder for two minutes for interference eight minutes into period three, the inevitable happened.
Jere Innala's centre was deflected onto Kallgren by Max Friberg, but the goaltender failed to deal with the loose puck and Friberg tapped in a second goal for Frolunda.
Despite racking up six two-minute suspensions, Frolunda only allowed 17 shots on their goal, all of which were dealt with by Lars Johansson, meaning the visitors will take a 2-0 lead back to Gothenburg ahead of the second leg next Tuesday, 20th January.
Whether Frolunda get the job done or Brynas pull off a comeback, another SHL side could be awaiting them in the Final, after Lulea went to Switzerland and won 3-2 against EV Zug.
The Swiss side presented their guests with a pair of early powerplay chances, and though they couldn't make the most of them, Lulea kept pressing and went ahead late in the first period when Heikki Liedes got the puck out from under his feet and buried it past goaltender Leonardo Genoni.
1-0 was how things stayed until midway through the match, when Lulea's first penalty - interference by Isac Hedqvist - was punished on the powerplay by Zug's Jan Kovar.
However, Hedqvist more than atoned a couple of minutes later, after Oskar Engsund was penalised for holding the stick. Despite being a man down, Hedqvist put pressure on the home side and won the puck in the attacking zone before firing in a shorthanded goal to restore the lead.
Three minutes later, with their tails very much up, Lulea put themselves two goals ahead when Benjamin Tardif reacted quickest to a loose puck in the Zug zone and swept it beyond Genoni.
Another interference call, this time against Pontus Andreasson, allowed Tomas Tatar to pull a goal back and set up a nervy final 12 minutes, but Lulea held on for a crucial win and a one-goal lead to take back to northern Sweden for the second leg, which also will be played on 20th January.
Review all the stats from tonight's CHL Semi-final first legs on Flashscore.