Morris' early try and a conversion from Jordan Williams put the Scarlets in the driving seat at the interval, although Lewis Williams' penalty did at least cuit the deficit shortly before the break.
Five minutes into the second half centre Ryan Evans nipped over for a try Williams improved and though two penalties from Jordan Williams and a reply from namesake Lewis saw the sides locked together at 13-13, it was the Blues who won the day thanks to Lewis Williams' 67th minute kick.
North team manager Nigel Way said; "It's just reward for the coaching team led by Dale McIntosh and for the boys who worked so hard during the regular season to finish on top of the qualifying group.
"We struggled to get to grips with the Scarlets in the first half and their interval lead was fully justified. However, after that, we played some good rugby and Lewis's late kick gave us the win.
"I'm delighted that we have finished the season as strongly as we started it."