As it became clear that the undead were not going to breach the border, even if the defenders ran out of ammunition, the gathered guardians began to split into groups.
One was the border leaders, who had initially intended to fly back home, but now gathered around the barrier core, adding mana to it as needed and checking for signs that there were breaks in the line.
It was still slowly expanding, but not everywhere along the border was currently under attack. So, most of the portions going up at that moment were in areas that were currently safe, and just following the order to erect the barrier for future safety, while the passing Fae built a defensive wall along the border.