The stage was set for Brisbane's horror injury night when Queensland winger Corey Oates was heavily concussed in a sickening collision with teammate Anthony Milford in the 21st minute.
Forwards Sam Thaiday and Jai Arrow (both concussion) joined him on the sideline by the second half.
Yet Brisbane somehow still racked up their seventh-straight finals win at Suncorp Stadium to book a grand final qualifier with the Storm.
The Panthers season is over despite also bravely battling on with injury.
They lost five-eighth Tyrone May (knee) on the stroke of halftime in a huge blow to a Penrith side without captain Matt Moylan for the finals.
Penrith halfback Nathan Cleary may have earned Johnathan Thurston comparisons before the match from Brisbane but even he couldn't spark the visitors with May sidelined.
Brisbane had already copped a major blow to their quest to end their longest title drought when fullback Boyd pulled out of the sudden-death clash after opting to sit out a second week with a hamstring injury.
And the Broncos were reeling after Oates was floored in friendly fire with Milford.
The 38,623-strong crowd were hushed when Oates lay motionless for minutes after being accidentally taken high by Milford running onto a pass and had to be taken off by a medicab.
Oates had opened the scoring when he snapped up a Ben Hunt pass to run 55m and give Brisbane a 6-0 halftime lead.
David Mead was outstanding as Oates' wing replacement while centre Tautau Moga monstered the Panthers in attack as Brisbane jumped to a 12-0 lead by the 47th minute when centre James Roberts scored.
Penrith ensured a nervous finish when impressive prop Reagan Campbell-Gillard marched up the middle to score in the 64th minute and cut the deficit to 12-6.
Kiwi Winger Jordan Kahu's 70th minute field goal iced the result.
Wayne Bennett chipped away at his lopsided record against the man he replaced as Brisbane coach in 2014 - Penrith's Anthony Griffin - with his third win in 12 games.
It was Brisbane's first week-two finals win since 2011.
Brisbane second rower Matt Gillett may come under scrutiny for a 23rd minute attempted trip of May.