Grain cropping. Also water mills. Some for electrical power,  most are for typical grain milling.  Vodahmin can stretch for miles, and make use of the moving air and gases of the earth for plants that need to breathe.  The Vodamin connecting the first Unahzals stretches over 450 miles long, waxing anywhere from a quarter mile to several miles wide, and webbing off in various directions at intersections for at least equal length.  The estimated size of the Vodamin production field is somewhere in the range of 5,000 square miles/3200000 acres, or roughly the size of Connecticut. In comparison to crop production in the real world,  The average yield per acre of winter wheat is 82.0 (2.46 tons, 4920 lbs) bushels - (estimated 262,400,000 bushels - 7,872,000tons). One bushel of wheat yields 42lbs of white flour/60 pounds of whole-wheat flour. A bushel of wheat yields 42 one-and-a-half pound commercial loaves of white bread OR about 90 one-pound loaves of whole wheat bread. In production standard, in raw bread conversion, that's 11,020,800,000 loaves a year.  Of course, it won't go straight to bread, because it isn't all wheat, nor typical wheat, and flour types will be needed, etc.  This is just to get a scope of the substantial support created. Even if, in theory, the kingdom some day got to some 30 million people, the first Vodahmin has enough room to service 367 loaves to each person per year, more than one per day.

Excess composting and dry and depleted dirts are pushed out from Unahzaals into Vodahmin to be sorted by the workers, with excess compost used to lay the subterranean fields and useless silt either reconditioned or motioned into later explained avenues. The true police forces, guards and actual military, named the Ronax, of Xorvintaal exist in and tend the Vodahmin. Ronax are discussed elsewhere.