West Coast closed the second place on the AFL ladder with an airy victory of 26 points on Brisbane.
It was an ideal pre-final tune-up for the Eagles, who canceled a Lions outfit that had last saved one of their sloppy performance the whole year.
The 14.14 (98) to 11.6 (72) result on Sunday afternoon will cause West Coast to play two finals in Optus Stadium, starting with a qualifying final against Collingwood.
The Lions lacked balance when the game was on the line and just as many as 44 points followed three-quarters.
West Coast midfield trio Dom Sheed (30 sales), Jack Redden (29 sales) and Luke Shuey (27 sales) rebelled and contributed 21 of the 42 clearances.
In front Jack Darling kicked four goals, while Jamie Cripps and Liam Ryan each scored three chips.
For Brisbane, it was a disappointing end to a promising season.
They wanted to shape the top four in their final assignment in 2018, and given the huge improvements they've made to coach Chris Fagan's second campaign at the helm, it was rightly billed as a dangerous game for the Eagles.
In the first quarter it certainly looked like one, with the leading alternating hands six times because players approached the smoothness after a morning with heavy rain showers.
But West Coast killed the game in only the second run, started four goals and limited the Lions to two rankings to get 35 points during the long break.
Then they were never really in doubt, although Brisbane scored in the last quarter and defeated West Coast with four goals to give the 16.367-strong Gabba crowd something to cheer.
Dayne Beams was the best for the Lions with a game-high 32 touches.
But the man who replaced him as captain, Dayne Zorko, struggled again under the pressure of a heavy tag and Mark Hutchings held only 16 sales.