That’s true about the weight. There are some 50lbs shot for the anti personnel catapults. But they mostly use bolt throwers against small groups of infantry.
Kerkly, who can still communicate, plans this. He wants the lantern archons to go to the 50 pound shot (teleporting). They can teleport items up to 50 pounds. They will teleport the shot to about 500 feet up and the drop over and ahead of the northern most wug army (I believe they have not been hindered yet.
They can unleash that storm every other round. Each ball will take 1 round (just under 6 seconds to be precise) to hit the ground at 120 miles an hour. They don't aim for particular targets, just hit the area of the horde.