The Blues have advanced to the Far West football A grade preliminary final following a 27-point triumph over Thevenard in Saturday's first semi final.
It took until the second quarter for the Blues to get going, but they continued their good run of form to win 11-8 (74) to 6-11 (47).
Thomas Clayton led the way with three goals and both Jaxon Bennett and Trevor Peel booted two, while Thevenard pair Dom Denton and Beau Halbert kicked two goals apiece.
Thevenard had the better of a tight first quarter and kicked the only goal of the term to lead by six points at the first break.
The game turned in the second quarter as the Blues enjoyed more run from midfield to kick four successive goals - Bennett leading the charge with the first two - to break clear, although the Magpies grabbed a late goal to remain in the hunt and three goals adrift.
Thevenard hoped to get off to a good start in the third term, instead the Blues grabbed the opening two goals and kicked four to two overall to increase the margin to 29 points.
Kicking the first goal in the final quarter gave the Magpies a sniff, but each time they found the middle the Blues responded to win a fourth match from the past five outings.
This weekend sees Western United and Koonibba meet at Penong, with the winner to advance to the grand final and the loser to have a second chance against the Blues.
In the B grade, Thevenard reached the preliminary final thanks to a commanding win against the Blues.
The Magpies dominated for three quarters to win by 73 points, as the match ended 12-13 (85) to 2-0 (12).
Thevy showed from the start that they meant business with the loser to say goodbye for 2019 and had seven scoring shots to none in the first quarter, but with five behinds could not completely capitalise.
The Blues hit back once play resumed with two goals to one to close the gap to 11 points by half-time, yet it was all Thevenard from that point.
The Magpies kicked six goals in a punishing third term and three goals in the final quarter, while the Blues failed to add to their tally.
Jacob Grills enjoyed his day out with four goals, while Neville Bryant and Brenton Mullan kicked three apiece.
Jaiden Hansen kicked both goals for the Blues.
Thevenard will meet the loser of this Saturday's match between Koonibba and Western United.
The under 17s clash between Western United and the Blues went the way of Westies by 88 points.
The Tigers started well and were never troubled to win 18-7 (115) to 4-3 (27).
Isaak Kugena was dominant in the forward 50 to kick seven goals, while teammate Brent Dunn added six.
Westies kicked four goals in each of the opening two quarters to lead by 45 points at half-time.
They continued to build the lead, finishing with seven fourth-quarter goals.
Koonibba and Thevenard will meet in this weekend's second semi final with a grand final spot on the line.
Western United thrashed Thevenard by 79 points in the under 14 clash.
The Magpies did not get on the board as it finished 12-7 (79) to 0-0 (0).
Jay Polkinghorne booted five goals for Western United and Zaide Thomas grabbed four.
The Blues and Koonibba meet this Saturday in the second semi final.