The reason was simple. Dwarven artillery was designed to fire at walls, not at the sky. Angling bombards upward with enough precision to concentrate fire on the apex of a dome hundreds of meters above the ground was a logistical impossibility. The shells would scatter. The rolling cadence that made their bombardment effective relied on hitting the same zone repeatedly, and that zone needed to be a flat face, not a curved point at the top of the world.
Perhaps the best alternative was a mage. In theory, a single mage with enough firepower could bypass the artillery entirely and strike the apex directly.
In theory.
Because that mage would need to fly. Not levitate for a few seconds or ride a summoned creature, but sustain true, stable flight at altitude long enough to deliver repeated strikes.
